| Message ID | 20191011110709.2764-1-christoffer.dall@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Improve handling of stage 2 aborts without instruction decode | expand |
Hi Christoffer, On Fri, 11 Oct 2019 12:07:04 +0100, Christoffer Dall <christoffer.dall@arm.com> wrote: > > When a guest accesses memory outside the memory slots, KVM usually > bounces the access back to userspace with KVM_EXIT_MMIO. However, on > arm/arm64 systems, certain load/store instructions did not provide > decoding info for the hypervisor to emulate the instruction, and in this > case KVM has rather rudely returned -ENOSYS and printed a not overly > helpful error message: > > load/store instruction decoding not implemented > > This patch series improves the error message and allows userspace to be > notified of this event instead of receiving -ENOSYS, and also allows > userspace to ask KVM to inject an external abort to the guest, which it > can use for any memory access that it either cannot handle. > > One remaining case which this patch set does not address is if the guest > accesses an in-kernel emulated device, such as the VGIC, but using a > load/store instruction which doesn't provide decode info. With these > patches, this will return to userspace for it to handle, but there's no > way for userspace to return the decoding information to KVM and have KVM > complete the access to the in-kernel emulated device. I have no plans > to address this limitation. You had some pending comments on patch 2, and you seem to indicate that you would respin the series. Do you have plans to do so in the coming days? I'd like to put that series into -next, but I can either wait for your respin, or queue it as it is and apply fixes on top. Please let me know what you prefer. Thanks, M.
On Sun, Oct 20, 2019 at 11:25:24AM +0100, Marc Zyngier wrote: > Hi Christoffer, > > On Fri, 11 Oct 2019 12:07:04 +0100, > Christoffer Dall <christoffer.dall@arm.com> wrote: > > > > When a guest accesses memory outside the memory slots, KVM usually > > bounces the access back to userspace with KVM_EXIT_MMIO. However, on > > arm/arm64 systems, certain load/store instructions did not provide > > decoding info for the hypervisor to emulate the instruction, and in this > > case KVM has rather rudely returned -ENOSYS and printed a not overly > > helpful error message: > > > > load/store instruction decoding not implemented > > > > This patch series improves the error message and allows userspace to be > > notified of this event instead of receiving -ENOSYS, and also allows > > userspace to ask KVM to inject an external abort to the guest, which it > > can use for any memory access that it either cannot handle. > > > > One remaining case which this patch set does not address is if the guest > > accesses an in-kernel emulated device, such as the VGIC, but using a > > load/store instruction which doesn't provide decode info. With these > > patches, this will return to userspace for it to handle, but there's no > > way for userspace to return the decoding information to KVM and have KVM > > complete the access to the in-kernel emulated device. I have no plans > > to address this limitation. > > You had some pending comments on patch 2, and you seem to indicate > that you would respin the series. Do you have plans to do so in the > coming days? I'd like to put that series into -next, but I can either > wait for your respin, or queue it as it is and apply fixes on top. > I think those for v2 and this is v3 which should address those concerns. Did I miss something or manage to confuse mysel here? Thanks, Christoffer
On 2019-10-21 14:37, Christoffer Dall wrote: > On Sun, Oct 20, 2019 at 11:25:24AM +0100, Marc Zyngier wrote: >> Hi Christoffer, >> >> On Fri, 11 Oct 2019 12:07:04 +0100, >> Christoffer Dall <christoffer.dall@arm.com> wrote: >> > >> > When a guest accesses memory outside the memory slots, KVM usually >> > bounces the access back to userspace with KVM_EXIT_MMIO. However, >> on >> > arm/arm64 systems, certain load/store instructions did not provide >> > decoding info for the hypervisor to emulate the instruction, and >> in this >> > case KVM has rather rudely returned -ENOSYS and printed a not >> overly >> > helpful error message: >> > >> > load/store instruction decoding not implemented >> > >> > This patch series improves the error message and allows userspace >> to be >> > notified of this event instead of receiving -ENOSYS, and also >> allows >> > userspace to ask KVM to inject an external abort to the guest, >> which it >> > can use for any memory access that it either cannot handle. >> > >> > One remaining case which this patch set does not address is if the >> guest >> > accesses an in-kernel emulated device, such as the VGIC, but using >> a >> > load/store instruction which doesn't provide decode info. With >> these >> > patches, this will return to userspace for it to handle, but >> there's no >> > way for userspace to return the decoding information to KVM and >> have KVM >> > complete the access to the in-kernel emulated device. I have no >> plans >> > to address this limitation. >> >> You had some pending comments on patch 2, and you seem to indicate >> that you would respin the series. Do you have plans to do so in the >> coming days? I'd like to put that series into -next, but I can >> either >> wait for your respin, or queue it as it is and apply fixes on top. >> > > I think those for v2 and this is v3 which should address those > concerns. > Did I miss something or manage to confuse mysel here? Gah! No, it looks like the mistake is mine. I've mixed the two series in my Inbox, and the result is a total brain-fart. Ignore me. I'll queue these patches ASAP. Thanks, M.