| Message ID | 20240325164021.3229-2-jszhang@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | riscv: improve nommu and timer-clint | expand |
On 3/25/24 9:40 AM, Jisheng Zhang wrote: > Currently, PAGE_OFFSET is hardcoded as 0x8000_0000, it works fine since > there's only one nommu platform in the mainline. However, there are > many cases where the (S)DRAM base address isn't 0x8000_0000, so remove > the hardcoding value, and introduce DRAM_BASE which will be set by > users during configuring. DRAM_BASE is 0x8000_0000 by default. > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > --- > arch/riscv/Kconfig | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 7895c77545f1..afd51dbdc253 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -247,10 +247,16 @@ config MMU > Select if you want MMU-based virtualised addressing space > support by paged memory management. If unsure, say 'Y'. > > +if !MMU > +config DRAM_BASE > + hex '(S)DRAM Base Address' > + default 0x80000000 > +endif > + > config PAGE_OFFSET > hex > default 0xC0000000 if 32BIT && MMU > - default 0x80000000 if !MMU > + default DRAM_BASE if !MMU > default 0xff60000000000000 if 64BIT > > config KASAN_SHADOW_OFFSET > Thanks for this patch. I did something similar in my local nommu linux-6.8 tree in order to run it on the S7 hart of JH7110. I have another suggestion for you. Perhaps we should also make TASK_SIZE configurable, and let it default to `0xffffffff if 32BIT && !MMU` and `DRAM_BASE + DRAM_SIZE if 64BIT && !MMU`. Currently TASK_SIZE is effectively `0xffffffff if !MMU`, which doesn't work if I run rv64 linux-nommu with DDR that spans across 4G boundary. I see there's another patchset that tries to define TASK_SIZE_MAX for __access_ok(). Looks like that only affects the MMU case, and NOMMU is not touched. My aforementioned change won't conflict with it should it get merged. Bo
On Mon, Mar 25, 2024 at 03:46:01PM -0700, Bo Gan wrote: > On 3/25/24 9:40 AM, Jisheng Zhang wrote: > > Currently, PAGE_OFFSET is hardcoded as 0x8000_0000, it works fine since > > there's only one nommu platform in the mainline. However, there are > > many cases where the (S)DRAM base address isn't 0x8000_0000, so remove > > the hardcoding value, and introduce DRAM_BASE which will be set by > > users during configuring. DRAM_BASE is 0x8000_0000 by default. > > > > Signed-off-by: Jisheng Zhang <jszhang@kernel.org> > > --- > > arch/riscv/Kconfig | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > > index 7895c77545f1..afd51dbdc253 100644 > > --- a/arch/riscv/Kconfig > > +++ b/arch/riscv/Kconfig > > @@ -247,10 +247,16 @@ config MMU > > Select if you want MMU-based virtualised addressing space > > support by paged memory management. If unsure, say 'Y'. > > +if !MMU > > +config DRAM_BASE > > + hex '(S)DRAM Base Address' > > + default 0x80000000 > > +endif > > + > > config PAGE_OFFSET > > hex > > default 0xC0000000 if 32BIT && MMU > > - default 0x80000000 if !MMU > > + default DRAM_BASE if !MMU > > default 0xff60000000000000 if 64BIT > > config KASAN_SHADOW_OFFSET > > > > Thanks for this patch. I did something similar in my local nommu > linux-6.8 tree in order to run it on the S7 hart of JH7110. I have > another suggestion for you. Perhaps we should also make TASK_SIZE > configurable, and let it default to `0xffffffff if 32BIT && !MMU` > and `DRAM_BASE + DRAM_SIZE if 64BIT && !MMU`. Currently TASK_SIZE > is effectively `0xffffffff if !MMU`, which doesn't work if I run > rv64 linux-nommu with DDR that spans across 4G boundary. I must admit that there's such nommu linux with 4GB DDR case in theory, but it doesn't exist in real world: who will make such strange platform ;) But anyway this improvement can be made when the patchset talking about TASK_SIZE_MAX is settled down. > > I see there's another patchset that tries to define TASK_SIZE_MAX > for __access_ok(). Looks like that only affects the MMU case, and > NOMMU is not touched. My aforementioned change won't conflict with > it should it get merged. > > Bo
On 2024-03-25 8:28 PM, Jisheng Zhang wrote: > On Mon, Mar 25, 2024 at 03:46:01PM -0700, Bo Gan wrote: >> On 3/25/24 9:40 AM, Jisheng Zhang wrote: >>> Currently, PAGE_OFFSET is hardcoded as 0x8000_0000, it works fine since >>> there's only one nommu platform in the mainline. However, there are >>> many cases where the (S)DRAM base address isn't 0x8000_0000, so remove >>> the hardcoding value, and introduce DRAM_BASE which will be set by >>> users during configuring. DRAM_BASE is 0x8000_0000 by default. >>> >>> Signed-off-by: Jisheng Zhang <jszhang@kernel.org> >>> --- >>> arch/riscv/Kconfig | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig >>> index 7895c77545f1..afd51dbdc253 100644 >>> --- a/arch/riscv/Kconfig >>> +++ b/arch/riscv/Kconfig >>> @@ -247,10 +247,16 @@ config MMU >>> Select if you want MMU-based virtualised addressing space >>> support by paged memory management. If unsure, say 'Y'. >>> +if !MMU >>> +config DRAM_BASE >>> + hex '(S)DRAM Base Address' >>> + default 0x80000000 >>> +endif >>> + >>> config PAGE_OFFSET >>> hex Another option would be to change this to: hex "DRAM Base Address" if !MMU so the prompt is only visible for NOMMU, but we don't need a new symbol. >>> default 0xC0000000 if 32BIT && MMU >>> - default 0x80000000 if !MMU >>> + default DRAM_BASE if !MMU >>> default 0xff60000000000000 if 64BIT >>> config KASAN_SHADOW_OFFSET >>> >> >> Thanks for this patch. I did something similar in my local nommu >> linux-6.8 tree in order to run it on the S7 hart of JH7110. I have >> another suggestion for you. Perhaps we should also make TASK_SIZE >> configurable, and let it default to `0xffffffff if 32BIT && !MMU` >> and `DRAM_BASE + DRAM_SIZE if 64BIT && !MMU`. Currently TASK_SIZE >> is effectively `0xffffffff if !MMU`, which doesn't work if I run >> rv64 linux-nommu with DDR that spans across 4G boundary. > > I must admit that there's such nommu linux with 4GB DDR case in > theory, but it doesn't exist in real world: who will make such > strange platform ;) But anyway this improvement can be made when > the patchset talking about TASK_SIZE_MAX is settled down. This case is quite easy to hit with QEMU :) In fact I sent a patch making this exact change: https://lore.kernel.org/linux-riscv/20240227003630.3634533-2-samuel.holland@sifive.com/ It's not really related to TASK_SIZE_MAX. access_ok() is a no-op on NOMMU, because you can't prevent userspace from poking the kernel anyway. Regards, Samuel
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 7895c77545f1..afd51dbdc253 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -247,10 +247,16 @@ config MMU Select if you want MMU-based virtualised addressing space support by paged memory management. If unsure, say 'Y'. +if !MMU +config DRAM_BASE + hex '(S)DRAM Base Address' + default 0x80000000 +endif + config PAGE_OFFSET hex default 0xC0000000 if 32BIT && MMU - default 0x80000000 if !MMU + default DRAM_BASE if !MMU default 0xff60000000000000 if 64BIT config KASAN_SHADOW_OFFSET
Currently, PAGE_OFFSET is hardcoded as 0x8000_0000, it works fine since there's only one nommu platform in the mainline. However, there are many cases where the (S)DRAM base address isn't 0x8000_0000, so remove the hardcoding value, and introduce DRAM_BASE which will be set by users during configuring. DRAM_BASE is 0x8000_0000 by default. Signed-off-by: Jisheng Zhang <jszhang@kernel.org> --- arch/riscv/Kconfig | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)