| Message ID | 20210310003216.410037-1-msalter@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: mm: fix runtime fallback to 48-bt VA when 52-bit VA is enabled | expand |
On Tue, Mar 09, 2021 at 07:32:16PM -0500, Mark Salter wrote: > I ran into an early boot soft lockup on a Qualcomm Amberwing using a v5.11 > kernel configured for 52-bit VA. This turned into a panic with a v5.12-rc2 > kernel. > > The problem is that when we fall back to 48-bit VA, idmap_t0sz is not > updated. Later, the kvm hypervisor uses idmap_t0sz to set its tcr_el2 and > hangs (v5.11). After commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 > from __cpu_set_tcr_t0sz()"), the kernel panics when trying to use the idmap > to call idmap_cpu_replace_ttbr1(). > > Oddly, other systems (thunderX2 and Ampere eMag) which don't support 52-bit > VA seem to handle the setting of an unsupported t0sz without any apparent > problems. Indeed, if one reads back the tcr written with t0sz==12, the > value read has t0sz==16. Not so with Amberwing. Nice, you have one of those elusive platforms! > Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") > Signed-off-by: Mark Salter <msalter@redhat.com> > --- > arch/arm64/kernel/head.S | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 66b0e0b66e31..2bcbbb26292e 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -291,6 +291,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > */ > adrp x0, idmap_pg_dir > adrp x3, __idmap_text_start // __pa(__idmap_text_start) > + mov x4, TCR_T0SZ(VA_BITS) > > #ifdef CONFIG_ARM64_VA_BITS_52 > mrs_s x6, SYS_ID_AA64MMFR2_EL1 > @@ -299,6 +300,13 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > cbnz x6, 1f > #endif > mov x5, #VA_BITS_MIN > +#ifdef CONFIG_ARM64_VA_BITS_52 > + mov x4, TCR_T0SZ(VA_BITS_MIN) > + adr_l x6, idmap_t0sz > + str x4, [x6] > + dmb sy > + dc ivac, x6 // Invalidate potentially stale cache line > +#endif > 1: > adr_l x6, vabits_actual > str x5, [x6] > @@ -319,7 +327,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > */ > adrp x5, __idmap_text_end > clz x5, x5 > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > + cmp x5, x4 // default T0SZ small enough? > b.ge 1f // .. then skip VA range extension Could we instead have the default value be 48-bit, and then avoid having to update the variable in both cases? e.g. something along the lines of the entirely untested diff below? Cheers, Will --->8 diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 66b0e0b66e31..fb795123896f 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -319,7 +319,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ adrp x5, __idmap_text_end clz x5, x5 - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? + cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? b.ge 1f // .. then skip VA range extension adr_l x6, idmap_t0sz diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 3802cfbdd20d..4c5603c41870 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -40,7 +40,7 @@ #define NO_BLOCK_MAPPINGS BIT(0) #define NO_CONT_MAPPINGS BIT(1) -u64 idmap_t0sz = TCR_T0SZ(VA_BITS); +u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; u64 __section(".mmuoff.data.write") vabits_actual;
On Wed, 10 Mar 2021 at 12:18, Will Deacon <will@kernel.org> wrote: > > On Tue, Mar 09, 2021 at 07:32:16PM -0500, Mark Salter wrote: > > I ran into an early boot soft lockup on a Qualcomm Amberwing using a v5.11 > > kernel configured for 52-bit VA. This turned into a panic with a v5.12-rc2 > > kernel. > > > > The problem is that when we fall back to 48-bit VA, idmap_t0sz is not > > updated. Later, the kvm hypervisor uses idmap_t0sz to set its tcr_el2 and > > hangs (v5.11). After commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 > > from __cpu_set_tcr_t0sz()"), the kernel panics when trying to use the idmap > > to call idmap_cpu_replace_ttbr1(). > > > > Oddly, other systems (thunderX2 and Ampere eMag) which don't support 52-bit > > VA seem to handle the setting of an unsupported t0sz without any apparent > > problems. Indeed, if one reads back the tcr written with t0sz==12, the > > value read has t0sz==16. Not so with Amberwing. > > Nice, you have one of those elusive platforms! > > > Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") > > Signed-off-by: Mark Salter <msalter@redhat.com> > > --- > > arch/arm64/kernel/head.S | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > index 66b0e0b66e31..2bcbbb26292e 100644 > > --- a/arch/arm64/kernel/head.S > > +++ b/arch/arm64/kernel/head.S > > @@ -291,6 +291,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > */ > > adrp x0, idmap_pg_dir > > adrp x3, __idmap_text_start // __pa(__idmap_text_start) > > + mov x4, TCR_T0SZ(VA_BITS) > > > > #ifdef CONFIG_ARM64_VA_BITS_52 > > mrs_s x6, SYS_ID_AA64MMFR2_EL1 > > @@ -299,6 +300,13 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > cbnz x6, 1f > > #endif > > mov x5, #VA_BITS_MIN > > +#ifdef CONFIG_ARM64_VA_BITS_52 > > + mov x4, TCR_T0SZ(VA_BITS_MIN) > > + adr_l x6, idmap_t0sz > > + str x4, [x6] > > + dmb sy > > + dc ivac, x6 // Invalidate potentially stale cache line > > +#endif > > 1: > > adr_l x6, vabits_actual > > str x5, [x6] > > @@ -319,7 +327,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > */ > > adrp x5, __idmap_text_end > > clz x5, x5 > > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > > + cmp x5, x4 // default T0SZ small enough? > > b.ge 1f // .. then skip VA range extension > > Could we instead have the default value be 48-bit, and then avoid having > to update the variable in both cases? e.g. something along the lines of > the entirely untested diff below? > There is one other occurrence that needs to be updated. I will have a stab at fixing this along these lines, and there are a couple of other things that need cleaning up. > --->8 > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 66b0e0b66e31..fb795123896f 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -319,7 +319,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > */ > adrp x5, __idmap_text_end > clz x5, x5 > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > + cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? > b.ge 1f // .. then skip VA range extension > > adr_l x6, idmap_t0sz > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 3802cfbdd20d..4c5603c41870 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -40,7 +40,7 @@ > #define NO_BLOCK_MAPPINGS BIT(0) > #define NO_CONT_MAPPINGS BIT(1) > > -u64 idmap_t0sz = TCR_T0SZ(VA_BITS); > +u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); > u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; > > u64 __section(".mmuoff.data.write") vabits_actual; > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
(+ James) On Wed, 10 Mar 2021 at 13:41, Ard Biesheuvel <ardb@kernel.org> wrote: > > On Wed, 10 Mar 2021 at 12:18, Will Deacon <will@kernel.org> wrote: > > > > On Tue, Mar 09, 2021 at 07:32:16PM -0500, Mark Salter wrote: > > > I ran into an early boot soft lockup on a Qualcomm Amberwing using a v5.11 > > > kernel configured for 52-bit VA. This turned into a panic with a v5.12-rc2 > > > kernel. > > > > > > The problem is that when we fall back to 48-bit VA, idmap_t0sz is not > > > updated. Later, the kvm hypervisor uses idmap_t0sz to set its tcr_el2 and > > > hangs (v5.11). After commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 > > > from __cpu_set_tcr_t0sz()"), the kernel panics when trying to use the idmap > > > to call idmap_cpu_replace_ttbr1(). > > > > > > Oddly, other systems (thunderX2 and Ampere eMag) which don't support 52-bit > > > VA seem to handle the setting of an unsupported t0sz without any apparent > > > problems. Indeed, if one reads back the tcr written with t0sz==12, the > > > value read has t0sz==16. Not so with Amberwing. > > > > Nice, you have one of those elusive platforms! > > > > > Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") > > > Signed-off-by: Mark Salter <msalter@redhat.com> > > > --- > > > arch/arm64/kernel/head.S | 10 +++++++++- > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > > index 66b0e0b66e31..2bcbbb26292e 100644 > > > --- a/arch/arm64/kernel/head.S > > > +++ b/arch/arm64/kernel/head.S > > > @@ -291,6 +291,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > */ > > > adrp x0, idmap_pg_dir > > > adrp x3, __idmap_text_start // __pa(__idmap_text_start) > > > + mov x4, TCR_T0SZ(VA_BITS) > > > > > > #ifdef CONFIG_ARM64_VA_BITS_52 > > > mrs_s x6, SYS_ID_AA64MMFR2_EL1 > > > @@ -299,6 +300,13 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > cbnz x6, 1f > > > #endif > > > mov x5, #VA_BITS_MIN > > > +#ifdef CONFIG_ARM64_VA_BITS_52 > > > + mov x4, TCR_T0SZ(VA_BITS_MIN) > > > + adr_l x6, idmap_t0sz > > > + str x4, [x6] > > > + dmb sy > > > + dc ivac, x6 // Invalidate potentially stale cache line > > > +#endif > > > 1: > > > adr_l x6, vabits_actual > > > str x5, [x6] > > > @@ -319,7 +327,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > */ > > > adrp x5, __idmap_text_end > > > clz x5, x5 > > > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > > > + cmp x5, x4 // default T0SZ small enough? > > > b.ge 1f // .. then skip VA range extension > > > > Could we instead have the default value be 48-bit, and then avoid having > > to update the variable in both cases? e.g. something along the lines of > > the entirely untested diff below? > > > > There is one other occurrence that needs to be updated. I will have a > stab at fixing this along these lines, and there are a couple of other > things that need cleaning up. > Actually, it seems like this breakage may have been introduced by commit 1401bef703a48cf79c674215f702a1435362beae Author: James Morse <james.morse@arm.com> Date: Mon Jan 25 14:19:12 2021 -0500 arm64: mm: Always update TCR_EL1 from __cpu_set_tcr_t0sz() as before that patch, we would never actually load idmap_t0sz into TCR on 52-bit VA kernels, AFAICT. It seems to me that the sanest approach is to default to a 48-bit idmap on 52-bit VA capable kernels (as Will suggests below). This means that the notion of 'extended ID map' now also includes cases where the ID map is smaller than the default VA_BITS range. However, the number of levels is going to be the same, so it does not affect the ID map page table population code in head.S. Also, __cpu_uses_extended_idmap() no longer has any users anyway, so we can remove it rather than bikeshed over a better name for it. > > > > --->8 > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > index 66b0e0b66e31..fb795123896f 100644 > > --- a/arch/arm64/kernel/head.S > > +++ b/arch/arm64/kernel/head.S > > @@ -319,7 +319,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > */ > > adrp x5, __idmap_text_end > > clz x5, x5 > > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > > + cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? > > b.ge 1f // .. then skip VA range extension > > > > adr_l x6, idmap_t0sz > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > index 3802cfbdd20d..4c5603c41870 100644 > > --- a/arch/arm64/mm/mmu.c > > +++ b/arch/arm64/mm/mmu.c > > @@ -40,7 +40,7 @@ > > #define NO_BLOCK_MAPPINGS BIT(0) > > #define NO_CONT_MAPPINGS BIT(1) > > > > -u64 idmap_t0sz = TCR_T0SZ(VA_BITS); > > +u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); > > u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; > > > > u64 __section(".mmuoff.data.write") vabits_actual; > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > linux-arm-kernel@lists.infradead.org > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Wed, 2021-03-10 at 14:29 +0100, Ard Biesheuvel wrote: > (+ James) > > On Wed, 10 Mar 2021 at 13:41, Ard Biesheuvel <ardb@kernel.org> wrote: > > > > On Wed, 10 Mar 2021 at 12:18, Will Deacon <will@kernel.org> wrote: > > > > > > On Tue, Mar 09, 2021 at 07:32:16PM -0500, Mark Salter wrote: > > > > I ran into an early boot soft lockup on a Qualcomm Amberwing using a v5.11 > > > > kernel configured for 52-bit VA. This turned into a panic with a v5.12-rc2 > > > > kernel. > > > > > > > > The problem is that when we fall back to 48-bit VA, idmap_t0sz is not > > > > updated. Later, the kvm hypervisor uses idmap_t0sz to set its tcr_el2 and > > > > hangs (v5.11). After commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 > > > > from __cpu_set_tcr_t0sz()"), the kernel panics when trying to use the idmap > > > > to call idmap_cpu_replace_ttbr1(). > > > > > > > > Oddly, other systems (thunderX2 and Ampere eMag) which don't support 52-bit > > > > VA seem to handle the setting of an unsupported t0sz without any apparent > > > > problems. Indeed, if one reads back the tcr written with t0sz==12, the > > > > value read has t0sz==16. Not so with Amberwing. > > > > > > Nice, you have one of those elusive platforms! > > > > > > > Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") > > > > Signed-off-by: Mark Salter <msalter@redhat.com> > > > > --- > > > > arch/arm64/kernel/head.S | 10 +++++++++- > > > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > > > index 66b0e0b66e31..2bcbbb26292e 100644 > > > > --- a/arch/arm64/kernel/head.S > > > > +++ b/arch/arm64/kernel/head.S > > > > @@ -291,6 +291,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > > */ > > > > adrp x0, idmap_pg_dir > > > > adrp x3, __idmap_text_start // __pa(__idmap_text_start) > > > > + mov x4, TCR_T0SZ(VA_BITS) > > > > > > > > #ifdef CONFIG_ARM64_VA_BITS_52 > > > > mrs_s x6, SYS_ID_AA64MMFR2_EL1 > > > > @@ -299,6 +300,13 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > > cbnz x6, 1f > > > > #endif > > > > mov x5, #VA_BITS_MIN > > > > +#ifdef CONFIG_ARM64_VA_BITS_52 > > > > + mov x4, TCR_T0SZ(VA_BITS_MIN) > > > > + adr_l x6, idmap_t0sz > > > > + str x4, [x6] > > > > + dmb sy > > > > + dc ivac, x6 // Invalidate potentially stale cache line > > > > +#endif > > > > 1: > > > > adr_l x6, vabits_actual > > > > str x5, [x6] > > > > @@ -319,7 +327,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > > */ > > > > adrp x5, __idmap_text_end > > > > clz x5, x5 > > > > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > > > > + cmp x5, x4 // default T0SZ small enough? > > > > b.ge 1f // .. then skip VA range extension > > > > > > Could we instead have the default value be 48-bit, and then avoid having > > > to update the variable in both cases? e.g. something along the lines of > > > the entirely untested diff below? > > > > > > > There is one other occurrence that needs to be updated. I will have a > > stab at fixing this along these lines, and there are a couple of other > > things that need cleaning up. > > > > Actually, it seems like this breakage may have been introduced by > > commit 1401bef703a48cf79c674215f702a1435362beae > Author: James Morse <james.morse@arm.com> > Date: Mon Jan 25 14:19:12 2021 -0500 > > arm64: mm: Always update TCR_EL1 from __cpu_set_tcr_t0sz() > > as before that patch, we would never actually load idmap_t0sz into TCR > on 52-bit VA kernels, AFAICT. Right, but even without that patch, the kvm hypervisor code would use idmap_t0sz for its mapping in cpu_init_hyp_mode(). That leads to a soft lockup rather than a panic with the above patch. I can boot on amberwing with the below patch. > > It seems to me that the sanest approach is to default to a 48-bit > idmap on 52-bit VA capable kernels (as Will suggests below). This > means that the notion of 'extended ID map' now also includes cases > where the ID map is smaller than the default VA_BITS range. However, > the number of levels is going to be the same, so it does not affect > the ID map page table population code in head.S. > > Also, __cpu_uses_extended_idmap() no longer has any users anyway, so > we can remove it rather than bikeshed over a better name for it. > > > > > > > > --->8 > > > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > > index 66b0e0b66e31..fb795123896f 100644 > > > --- a/arch/arm64/kernel/head.S > > > +++ b/arch/arm64/kernel/head.S > > > @@ -319,7 +319,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) > > > */ > > > adrp x5, __idmap_text_end > > > clz x5, x5 > > > - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? > > > + cmp x5, TCR_T0SZ(VA_BITS_MIN) // default T0SZ small enough? > > > b.ge 1f // .. then skip VA range extension > > > > > > adr_l x6, idmap_t0sz > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > > index 3802cfbdd20d..4c5603c41870 100644 > > > --- a/arch/arm64/mm/mmu.c > > > +++ b/arch/arm64/mm/mmu.c > > > @@ -40,7 +40,7 @@ > > > #define NO_BLOCK_MAPPINGS BIT(0) > > > #define NO_CONT_MAPPINGS BIT(1) > > > > > > -u64 idmap_t0sz = TCR_T0SZ(VA_BITS); > > > +u64 idmap_t0sz = TCR_T0SZ(VA_BITS_MIN); > > > u64 idmap_ptrs_per_pgd = PTRS_PER_PGD; > > > > > > u64 __section(".mmuoff.data.write") vabits_actual; > > > > > > > > > _______________________________________________ > > > linux-arm-kernel mailing list > > > linux-arm-kernel@lists.infradead.org > > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S index 66b0e0b66e31..2bcbbb26292e 100644 --- a/arch/arm64/kernel/head.S +++ b/arch/arm64/kernel/head.S @@ -291,6 +291,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ adrp x0, idmap_pg_dir adrp x3, __idmap_text_start // __pa(__idmap_text_start) + mov x4, TCR_T0SZ(VA_BITS) #ifdef CONFIG_ARM64_VA_BITS_52 mrs_s x6, SYS_ID_AA64MMFR2_EL1 @@ -299,6 +300,13 @@ SYM_FUNC_START_LOCAL(__create_page_tables) cbnz x6, 1f #endif mov x5, #VA_BITS_MIN +#ifdef CONFIG_ARM64_VA_BITS_52 + mov x4, TCR_T0SZ(VA_BITS_MIN) + adr_l x6, idmap_t0sz + str x4, [x6] + dmb sy + dc ivac, x6 // Invalidate potentially stale cache line +#endif 1: adr_l x6, vabits_actual str x5, [x6] @@ -319,7 +327,7 @@ SYM_FUNC_START_LOCAL(__create_page_tables) */ adrp x5, __idmap_text_end clz x5, x5 - cmp x5, TCR_T0SZ(VA_BITS) // default T0SZ small enough? + cmp x5, x4 // default T0SZ small enough? b.ge 1f // .. then skip VA range extension adr_l x6, idmap_t0sz
I ran into an early boot soft lockup on a Qualcomm Amberwing using a v5.11 kernel configured for 52-bit VA. This turned into a panic with a v5.12-rc2 kernel. The problem is that when we fall back to 48-bit VA, idmap_t0sz is not updated. Later, the kvm hypervisor uses idmap_t0sz to set its tcr_el2 and hangs (v5.11). After commit 1401bef703a4 ("arm64: mm: Always update TCR_EL1 from __cpu_set_tcr_t0sz()"), the kernel panics when trying to use the idmap to call idmap_cpu_replace_ttbr1(). Oddly, other systems (thunderX2 and Ampere eMag) which don't support 52-bit VA seem to handle the setting of an unsupported t0sz without any apparent problems. Indeed, if one reads back the tcr written with t0sz==12, the value read has t0sz==16. Not so with Amberwing. Fixes: 90ec95cda91a ("arm64: mm: Introduce VA_BITS_MIN") Signed-off-by: Mark Salter <msalter@redhat.com> --- arch/arm64/kernel/head.S | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)