| Message ID | 20220812000327.3154251-3-willmcvicker@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Lorenzo Pieralisi |
| Headers | show |
| Series | PCI: dwc: Add support for 64-bit MSI target addresses | expand |
On 08/11/2022, Will McVicker wrote: > Since not all devices require a 32-bit MSI address, add support to the > PCIe host driver to allow setting the DMA mask to 64-bits. This allows > kernels to disable ZONE_DMA32 and bounce buffering (swiotlb) without > risking not being able to get a 32-bit address during DMA allocation. > Basically, in the slim chance that there are no 32-bit allocations > available, the current PCIe host driver will fail to allocate the > msi_msg page due to a DMA address overflow (seen in [1]). With this > patch, the PCIe device can advertise 64-bit support via its MSI > capabilities to hint to the PCIe host driver to set the DMA mask to > 64-bits. > > [1] https://lore.kernel.org/all/Yo0soniFborDl7+C@google.com/ > > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Will McVicker <willmcvicker@google.com> > Reviewed-by: Rob Herring <robh@kernel.org> Acked-by: Jingoo Han <jingoohan1@gmail.com> > --- > drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++++++-- > drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++++ > drivers/pci/controller/dwc/pcie-designware.h | 1 + > 3 files changed, 21 insertions(+), 2 deletions(-) …..
On 2022-08-12 01:03, Will McVicker wrote: > Since not all devices require a 32-bit MSI address, add support to the > PCIe host driver to allow setting the DMA mask to 64-bits. This allows > kernels to disable ZONE_DMA32 and bounce buffering (swiotlb) without > risking not being able to get a 32-bit address during DMA allocation. > Basically, in the slim chance that there are no 32-bit allocations > available, the current PCIe host driver will fail to allocate the > msi_msg page due to a DMA address overflow (seen in [1]). With this > patch, the PCIe device can advertise 64-bit support via its MSI > capabilities to hint to the PCIe host driver to set the DMA mask to > 64-bits. It doesn't matter so much what the host's own capabilities are, though, what matters is that if you configure the MSI doorbell to decode some 64-bit address because you can, and later an endpoint shows up whose DMA mask doesn't reach that address, you've broken MSIs for that endpoint. While the host is probing, it cannot possibly know what future endpoint drivers may or may not do. Now, in the case where no ZONE_DMA{32} is configured, there's a fair likelihood that addressing-constrained endpoints are probably going to be broken in general, so that should not be fatal for the host. So *if* we fail to allocate a 32-bit MSI address, *then* we should fall back to a 64-bit one (when the host supports it), but to preserve compatibility we still must always attempt the 32-bit allocation first (oh, if there isn't a theme emerging here...) TBH this has come up enough times, and has enough subtle complexity, that I think it's high time to factor this all out into a helper between the PCI core code and the DMA API for "please give me a bus address that's guaranteed not to conflict with any valid DMA address". Thanks, Robin. > [1] https://lore.kernel.org/all/Yo0soniFborDl7+C@google.com/ > > Reported-by: kernel test robot <lkp@intel.com> > Signed-off-by: Will McVicker <willmcvicker@google.com> > Reviewed-by: Rob Herring <robh@kernel.org> > --- > drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++++++-- > drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++++ > drivers/pci/controller/dwc/pcie-designware.h | 1 + > 3 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > index 39f3b37d4033..d7831040791b 100644 > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > @@ -330,6 +330,8 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) > u64 *msi_vaddr; > int ret; > u32 ctrl, num_ctrls; > + bool msi_64bit = false; > + u16 msi_capabilities; > > for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++) > pp->irq_mask[ctrl] = ~0; > @@ -367,9 +369,17 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) > dw_chained_msi_isr, pp); > } > > - ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); > + msi_capabilities = dw_pcie_msi_capabilities(pci); > + if (msi_capabilities & PCI_MSI_FLAGS_ENABLE) > + msi_64bit = msi_capabilities & PCI_MSI_FLAGS_64BIT; > + > + dev_dbg(dev, "Setting MSI DMA mask to %s-bit.\n", > + msi_64bit ? "64" : "32"); > + ret = dma_set_mask_and_coherent(dev, msi_64bit ? > + DMA_BIT_MASK(64) : DMA_BIT_MASK(32)); > if (ret) > - dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n"); > + dev_warn(dev, "Failed to set DMA mask to %s-bit.\n", > + msi_64bit ? "64" : "32"); > > msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data, > GFP_KERNEL); > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > index c6725c519a47..650a7f22f9d0 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.c > +++ b/drivers/pci/controller/dwc/pcie-designware.c > @@ -82,6 +82,14 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap) > } > EXPORT_SYMBOL_GPL(dw_pcie_find_capability); > > +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci) > +{ > + u8 offset; > + > + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI); > + return dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS); > +} > + > static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start, > u8 cap) > { > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > index a871ae7eb59e..45fcdfc8c035 100644 > --- a/drivers/pci/controller/dwc/pcie-designware.h > +++ b/drivers/pci/controller/dwc/pcie-designware.h > @@ -332,6 +332,7 @@ void dw_pcie_version_detect(struct dw_pcie *pci); > > u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap); > u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap); > +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci); > > int dw_pcie_read(void __iomem *addr, int size, u32 *val); > int dw_pcie_write(void __iomem *addr, int size, u32 val);
On 08/23/2022, Robin Murphy wrote: > On 2022-08-12 01:03, Will McVicker wrote: > > Since not all devices require a 32-bit MSI address, add support to the > > PCIe host driver to allow setting the DMA mask to 64-bits. This allows > > kernels to disable ZONE_DMA32 and bounce buffering (swiotlb) without > > risking not being able to get a 32-bit address during DMA allocation. > > Basically, in the slim chance that there are no 32-bit allocations > > available, the current PCIe host driver will fail to allocate the > > msi_msg page due to a DMA address overflow (seen in [1]). With this > > patch, the PCIe device can advertise 64-bit support via its MSI > > capabilities to hint to the PCIe host driver to set the DMA mask to > > 64-bits. > > It doesn't matter so much what the host's own capabilities are, though, what > matters is that if you configure the MSI doorbell to decode some 64-bit > address because you can, and later an endpoint shows up whose DMA mask > doesn't reach that address, you've broken MSIs for that endpoint. While the > host is probing, it cannot possibly know what future endpoint drivers may or > may not do. > > Now, in the case where no ZONE_DMA{32} is configured, there's a fair > likelihood that addressing-constrained endpoints are probably going to be > broken in general, so that should not be fatal for the host. So *if* we fail > to allocate a 32-bit MSI address, *then* we should fall back to a 64-bit one > (when the host supports it), but to preserve compatibility we still must > always attempt the 32-bit allocation first (oh, if there isn't a theme > emerging here...) > > TBH this has come up enough times, and has enough subtle complexity, that I > think it's high time to factor this all out into a helper between the PCI > core code and the DMA API for "please give me a bus address that's > guaranteed not to conflict with any valid DMA address". > > Thanks, > Robin. Hi Robin, Thanks for the reviews! I'm happy with your suggestion of trying a 32-bit mask first for the reasons you mentioned. I have tested this out on my Pixel 6 and db845c and will push the updated patchset as v5. Regards, Will > > > [1] https://lore.kernel.org/all/Yo0soniFborDl7+C@google.com/ > > > > Reported-by: kernel test robot <lkp@intel.com> > > Signed-off-by: Will McVicker <willmcvicker@google.com> > > Reviewed-by: Rob Herring <robh@kernel.org> > > --- > > drivers/pci/controller/dwc/pcie-designware-host.c | 14 ++++++++++++-- > > drivers/pci/controller/dwc/pcie-designware.c | 8 ++++++++ > > drivers/pci/controller/dwc/pcie-designware.h | 1 + > > 3 files changed, 21 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c > > index 39f3b37d4033..d7831040791b 100644 > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c > > @@ -330,6 +330,8 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) > > u64 *msi_vaddr; > > int ret; > > u32 ctrl, num_ctrls; > > + bool msi_64bit = false; > > + u16 msi_capabilities; > > for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++) > > pp->irq_mask[ctrl] = ~0; > > @@ -367,9 +369,17 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) > > dw_chained_msi_isr, pp); > > } > > - ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); > > + msi_capabilities = dw_pcie_msi_capabilities(pci); > > + if (msi_capabilities & PCI_MSI_FLAGS_ENABLE) > > + msi_64bit = msi_capabilities & PCI_MSI_FLAGS_64BIT; > > + > > + dev_dbg(dev, "Setting MSI DMA mask to %s-bit.\n", > > + msi_64bit ? "64" : "32"); > > + ret = dma_set_mask_and_coherent(dev, msi_64bit ? > > + DMA_BIT_MASK(64) : DMA_BIT_MASK(32)); > > if (ret) > > - dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n"); > > + dev_warn(dev, "Failed to set DMA mask to %s-bit.\n", > > + msi_64bit ? "64" : "32"); > > msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data, > > GFP_KERNEL); > > diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c > > index c6725c519a47..650a7f22f9d0 100644 > > --- a/drivers/pci/controller/dwc/pcie-designware.c > > +++ b/drivers/pci/controller/dwc/pcie-designware.c > > @@ -82,6 +82,14 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap) > > } > > EXPORT_SYMBOL_GPL(dw_pcie_find_capability); > > +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci) > > +{ > > + u8 offset; > > + > > + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI); > > + return dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS); > > +} > > + > > static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start, > > u8 cap) > > { > > diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h > > index a871ae7eb59e..45fcdfc8c035 100644 > > --- a/drivers/pci/controller/dwc/pcie-designware.h > > +++ b/drivers/pci/controller/dwc/pcie-designware.h > > @@ -332,6 +332,7 @@ void dw_pcie_version_detect(struct dw_pcie *pci); > > u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap); > > u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap); > > +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci); > > int dw_pcie_read(void __iomem *addr, int size, u32 *val); > > int dw_pcie_write(void __iomem *addr, int size, u32 val);
diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c index 39f3b37d4033..d7831040791b 100644 --- a/drivers/pci/controller/dwc/pcie-designware-host.c +++ b/drivers/pci/controller/dwc/pcie-designware-host.c @@ -330,6 +330,8 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) u64 *msi_vaddr; int ret; u32 ctrl, num_ctrls; + bool msi_64bit = false; + u16 msi_capabilities; for (ctrl = 0; ctrl < MAX_MSI_CTRLS; ctrl++) pp->irq_mask[ctrl] = ~0; @@ -367,9 +369,17 @@ static int dw_pcie_msi_host_init(struct dw_pcie_rp *pp) dw_chained_msi_isr, pp); } - ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)); + msi_capabilities = dw_pcie_msi_capabilities(pci); + if (msi_capabilities & PCI_MSI_FLAGS_ENABLE) + msi_64bit = msi_capabilities & PCI_MSI_FLAGS_64BIT; + + dev_dbg(dev, "Setting MSI DMA mask to %s-bit.\n", + msi_64bit ? "64" : "32"); + ret = dma_set_mask_and_coherent(dev, msi_64bit ? + DMA_BIT_MASK(64) : DMA_BIT_MASK(32)); if (ret) - dev_warn(dev, "Failed to set DMA mask to 32-bit. Devices with only 32-bit MSI support may not work properly\n"); + dev_warn(dev, "Failed to set DMA mask to %s-bit.\n", + msi_64bit ? "64" : "32"); msi_vaddr = dmam_alloc_coherent(dev, sizeof(u64), &pp->msi_data, GFP_KERNEL); diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c index c6725c519a47..650a7f22f9d0 100644 --- a/drivers/pci/controller/dwc/pcie-designware.c +++ b/drivers/pci/controller/dwc/pcie-designware.c @@ -82,6 +82,14 @@ u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap) } EXPORT_SYMBOL_GPL(dw_pcie_find_capability); +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci) +{ + u8 offset; + + offset = dw_pcie_find_capability(pci, PCI_CAP_ID_MSI); + return dw_pcie_readw_dbi(pci, offset + PCI_MSI_FLAGS); +} + static u16 dw_pcie_find_next_ext_capability(struct dw_pcie *pci, u16 start, u8 cap) { diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h index a871ae7eb59e..45fcdfc8c035 100644 --- a/drivers/pci/controller/dwc/pcie-designware.h +++ b/drivers/pci/controller/dwc/pcie-designware.h @@ -332,6 +332,7 @@ void dw_pcie_version_detect(struct dw_pcie *pci); u8 dw_pcie_find_capability(struct dw_pcie *pci, u8 cap); u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap); +u16 dw_pcie_msi_capabilities(struct dw_pcie *pci); int dw_pcie_read(void __iomem *addr, int size, u32 *val); int dw_pcie_write(void __iomem *addr, int size, u32 val);