[ patch series targeting linux-5.4.y stable branch. ]
Creating a SEV-enabled guest with 380GB or more of memory causes a
cpu soft-hang in the host running 5.4 with the following stacktrace:
kernel: watchdog: BUG: soft lockup - CPU#214 stuck for 22s! [qemu-kvm:6424]
...
kernel: CPU: 214 PID: 6424 Comm: qemu-kvm Not tainted 5.4.183.stable #1
kernel: Hardware name: Oracle Corporation ORACLE SERVER E4-2c/Asm,MB
Tray,2U,E4-2c, BIOS 78014000 01/05/2022
kernel: RIP: 0010:clflush_cache_range+0x35/0x40
kernel: Code: f0 0f b7 15 63 53 99 01 89 f6 48 89 d0 48 f7 d8 48 21 f8 48 01 f7
48 39 f8 73 0c 66 0f ae 38 48 01 d0 48 39 c7 77 f4 0f ae f0 <5d> c3 66 0f 1f 84
00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 0f ae
kernel: RSP: 0018:ffffacba5e98fc30 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
kernel: RAX: ffffa1193cfbc000 RBX: ffffacbba4701000 RCX: 0000000000000000
kernel: RDX: 0000000000000040 RSI: 0000000000001000 RDI: ffffa1193cfbc000
kernel: RBP: ffffacba5e98fc30 R08: ffffacba5f44aca0 R09: ffffacbac3701000
kernel: R10: 0000000000000080 R11: ffff9f8500000af0 R12: ffffa18074a22f80
kernel: R13: ffffacbaf6889dd8 R14: ffffacba5f41d960 R15: ffffacba5f44aca0
kernel: FS: 00007fbe04321f00(0000) GS:ffffa1814ed80000(0000)
knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00007dfbebd7d000 CR3: 000801fb93d68002 CR4: 0000000000760ee0
kernel: PKRU: 55555554
kernel: Call Trace:
kernel: sev_clflush_pages.part.56+0x50/0x70 [kvm_amd]
kernel: svm_register_enc_region+0xe2/0x120 [kvm_amd]
kernel: kvm_arch_vm_ioctl+0x524/0xbd0 [kvm]
kernel: ? release_pages+0x212/0x430
kernel: ? __pagevec_lru_add_fn+0x192/0x2f0
kernel: kvm_vm_ioctl+0x9c/0x9d0 [kvm]
kernel: ? __lru_cache_add+0x59/0x70
kernel: ? lru_cache_add_active_or_unevictable+0x39/0xb0
kernel: ? __handle_mm_fault+0xa74/0xfd0
kernel: ? __switch_to_asm+0x34/0x70
kernel: do_vfs_ioctl+0xa9/0x640
kernel: ? __audit_syscall_entry+0xdd/0x130
kernel: ksys_ioctl+0x67/0x90
kernel: __x64_sys_ioctl+0x1a/0x20
kernel: do_syscall_64+0x60/0x1d0
kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9
kernel: RIP: 0033:0x7fbe0086563b
kernel: Code: 0f 1e fa 48 8b 05 4d b8 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff
ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff
73 01 c3 48 8b 0d 1d b8 2c 00 f7 d8 64 89 01 48
kernel: RSP: 002b:00007ffedf577418 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
kernel: RAX: ffffffffffffffda RBX: 00007dfbebe00000 RCX: 00007fbe0086563b
kernel: RDX: 00007ffedf577490 RSI: ffffffff8010aebb RDI: 000000000000000d
kernel: RBP: 000001c200000000 R08: ffffffffffffffff R09: ffffffffffffffff
kernel: R10: ffffffffffffffff R11: 0000000000000246 R12: 000001c200000000
kernel: R13: 00007dfbebe00000 R14: 0000000000000000 R15: 0000000000000000
The problem is the time spent flushing the caches when pinning memory for
SEV but it's unnecessary as it turns out - it is resolved by backporting
the following commits from Linux 5.10
e1ebb2b49048 KVM: SVM: Don't flush cache if hardware enforces cache coherency
across encryption domains
(conflict due to the function it fixed being moved in a refactoring in 5.7).
along with 3 other commits needed as dependencies.
(fbd5969d1ff2 avoids a conflict in 5866e9205b47)
fbd5969d1ff2 x86/cpufeatures: Mark two free bits in word 3
5866e9205b47 x86/cpu: Add hardware-enforced cache coherency as a CPUID feature
75d1cc0e05af x86/mm/pat: Don't flush cache if hardware enforces cache coherency across encryption domnains
Tested by creating various sized guests up to 1.8TB, with and without SEV enabled,
running a few benchmarks and passing kvm-unit-tests.
Borislav Petkov (1):
x86/cpufeatures: Mark two free bits in word 3
Krish Sadhukhan (3):
x86/cpu: Add hardware-enforced cache coherency as a CPUID feature
x86/mm/pat: Don't flush cache if hardware enforces cache coherency
across encryption domnains
KVM: SVM: Don't flush cache if hardware enforces cache coherency
across encryption domains
arch/x86/include/asm/cpufeatures.h | 2 ++
arch/x86/kernel/cpu/scattered.c | 1 +
arch/x86/kvm/svm.c | 3 ++-
arch/x86/mm/pageattr.c | 2 +-
4 files changed, 6 insertions(+), 2 deletions(-)
--
2.27.0
From: Krish Sadhukhan <[email protected]>
commit 5866e9205b47a983a77ebc8654949f696342f2ab upstream.
In some hardware implementations, coherency between the encrypted and
unencrypted mappings of the same physical page is enforced. In such a system,
it is not required for software to flush the page from all CPU caches in the
system prior to changing the value of the C-bit for a page. This hardware-
enforced cache coherency is indicated by EAX[10] in CPUID leaf 0x8000001f.
[ bp: Use one of the free slots in word 3. ]
Suggested-by: Tom Lendacky <[email protected]>
Signed-off-by: Krish Sadhukhan <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Liam Merwick <[email protected]>
---
arch/x86/include/asm/cpufeatures.h | 2 +-
arch/x86/kernel/cpu/scattered.c | 1 +
2 files changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index c934eb807f23..4705533eb88d 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -96,7 +96,7 @@
#define X86_FEATURE_SYSCALL32 ( 3*32+14) /* "" syscall in IA32 userspace */
#define X86_FEATURE_SYSENTER32 ( 3*32+15) /* "" sysenter in IA32 userspace */
#define X86_FEATURE_REP_GOOD ( 3*32+16) /* REP microcode works well */
-/* free ( 3*32+17) */
+#define X86_FEATURE_SME_COHERENT ( 3*32+17) /* "" AMD hardware-enforced cache coherency */
#define X86_FEATURE_LFENCE_RDTSC ( 3*32+18) /* "" LFENCE synchronizes RDTSC */
#define X86_FEATURE_ACC_POWER ( 3*32+19) /* AMD Accumulated Power Mechanism */
#define X86_FEATURE_NOPL ( 3*32+20) /* The NOPL (0F 1F) instructions */
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index adf9b71386ef..53004dbd55c4 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -41,6 +41,7 @@ static const struct cpuid_bit cpuid_bits[] = {
{ X86_FEATURE_MBA, CPUID_EBX, 6, 0x80000008, 0 },
{ X86_FEATURE_SME, CPUID_EAX, 0, 0x8000001f, 0 },
{ X86_FEATURE_SEV, CPUID_EAX, 1, 0x8000001f, 0 },
+ { X86_FEATURE_SME_COHERENT, CPUID_EAX, 10, 0x8000001f, 0 },
{ 0, 0, 0, 0, 0 }
};
--
2.27.0
On Fri, Mar 11, 2022 at 11:29:23AM +0000, Liam Merwick wrote:
> [ patch series targeting linux-5.4.y stable branch. ]
>
> Creating a SEV-enabled guest with 380GB or more of memory causes a
> cpu soft-hang in the host running 5.4 with the following stacktrace:
>
> kernel: watchdog: BUG: soft lockup - CPU#214 stuck for 22s! [qemu-kvm:6424]
> ...
> kernel: CPU: 214 PID: 6424 Comm: qemu-kvm Not tainted 5.4.183.stable #1
> kernel: Hardware name: Oracle Corporation ORACLE SERVER E4-2c/Asm,MB
> Tray,2U,E4-2c, BIOS 78014000 01/05/2022
> kernel: RIP: 0010:clflush_cache_range+0x35/0x40
> kernel: Code: f0 0f b7 15 63 53 99 01 89 f6 48 89 d0 48 f7 d8 48 21 f8 48 01 f7
> 48 39 f8 73 0c 66 0f ae 38 48 01 d0 48 39 c7 77 f4 0f ae f0 <5d> c3 66 0f 1f 84
> 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 0f ae
> kernel: RSP: 0018:ffffacba5e98fc30 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> kernel: RAX: ffffa1193cfbc000 RBX: ffffacbba4701000 RCX: 0000000000000000
> kernel: RDX: 0000000000000040 RSI: 0000000000001000 RDI: ffffa1193cfbc000
> kernel: RBP: ffffacba5e98fc30 R08: ffffacba5f44aca0 R09: ffffacbac3701000
> kernel: R10: 0000000000000080 R11: ffff9f8500000af0 R12: ffffa18074a22f80
> kernel: R13: ffffacbaf6889dd8 R14: ffffacba5f41d960 R15: ffffacba5f44aca0
> kernel: FS: 00007fbe04321f00(0000) GS:ffffa1814ed80000(0000)
> knlGS:0000000000000000
> kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> kernel: CR2: 00007dfbebd7d000 CR3: 000801fb93d68002 CR4: 0000000000760ee0
> kernel: PKRU: 55555554
> kernel: Call Trace:
> kernel: sev_clflush_pages.part.56+0x50/0x70 [kvm_amd]
> kernel: svm_register_enc_region+0xe2/0x120 [kvm_amd]
> kernel: kvm_arch_vm_ioctl+0x524/0xbd0 [kvm]
> kernel: ? release_pages+0x212/0x430
> kernel: ? __pagevec_lru_add_fn+0x192/0x2f0
> kernel: kvm_vm_ioctl+0x9c/0x9d0 [kvm]
> kernel: ? __lru_cache_add+0x59/0x70
> kernel: ? lru_cache_add_active_or_unevictable+0x39/0xb0
> kernel: ? __handle_mm_fault+0xa74/0xfd0
> kernel: ? __switch_to_asm+0x34/0x70
> kernel: do_vfs_ioctl+0xa9/0x640
> kernel: ? __audit_syscall_entry+0xdd/0x130
> kernel: ksys_ioctl+0x67/0x90
> kernel: __x64_sys_ioctl+0x1a/0x20
> kernel: do_syscall_64+0x60/0x1d0
> kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9
> kernel: RIP: 0033:0x7fbe0086563b
> kernel: Code: 0f 1e fa 48 8b 05 4d b8 2c 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff
> ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff
> 73 01 c3 48 8b 0d 1d b8 2c 00 f7 d8 64 89 01 48
> kernel: RSP: 002b:00007ffedf577418 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> kernel: RAX: ffffffffffffffda RBX: 00007dfbebe00000 RCX: 00007fbe0086563b
> kernel: RDX: 00007ffedf577490 RSI: ffffffff8010aebb RDI: 000000000000000d
> kernel: RBP: 000001c200000000 R08: ffffffffffffffff R09: ffffffffffffffff
> kernel: R10: ffffffffffffffff R11: 0000000000000246 R12: 000001c200000000
> kernel: R13: 00007dfbebe00000 R14: 0000000000000000 R15: 0000000000000000
>
> The problem is the time spent flushing the caches when pinning memory for
> SEV but it's unnecessary as it turns out - it is resolved by backporting
> the following commits from Linux 5.10
>
> e1ebb2b49048 KVM: SVM: Don't flush cache if hardware enforces cache coherency
> across encryption domains
> (conflict due to the function it fixed being moved in a refactoring in 5.7).
>
> along with 3 other commits needed as dependencies.
> (fbd5969d1ff2 avoids a conflict in 5866e9205b47)
>
> fbd5969d1ff2 x86/cpufeatures: Mark two free bits in word 3
> 5866e9205b47 x86/cpu: Add hardware-enforced cache coherency as a CPUID feature
> 75d1cc0e05af x86/mm/pat: Don't flush cache if hardware enforces cache coherency across encryption domnains
>
> Tested by creating various sized guests up to 1.8TB, with and without SEV enabled,
> running a few benchmarks and passing kvm-unit-tests.
>
>
> Borislav Petkov (1):
> x86/cpufeatures: Mark two free bits in word 3
>
> Krish Sadhukhan (3):
> x86/cpu: Add hardware-enforced cache coherency as a CPUID feature
> x86/mm/pat: Don't flush cache if hardware enforces cache coherency
> across encryption domnains
> KVM: SVM: Don't flush cache if hardware enforces cache coherency
> across encryption domains
>
> arch/x86/include/asm/cpufeatures.h | 2 ++
> arch/x86/kernel/cpu/scattered.c | 1 +
> arch/x86/kvm/svm.c | 3 ++-
> arch/x86/mm/pageattr.c | 2 +-
> 4 files changed, 6 insertions(+), 2 deletions(-)
>
> --
> 2.27.0
>
All now queued up, thanks!
greg k-h