| Message ID | 138b520fb83964782303b43ade4369cd181fdd9c.1739226950.git.ashish.kalra@amd.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | Fix broken SNP support with KVM module built-in | expand |
On Mon, Feb 10, 2025 at 10:54:18PM +0000, Ashish Kalra wrote: > From: Ashish Kalra <ashish.kalra@amd.com> > > Fix issues with enabling SNP host support and effectively SNP support > which is broken with respect to the KVM module being built-in. > > SNP host support is enabled in snp_rmptable_init() which is invoked as > device_initcall(). SNP check on IOMMU is done during IOMMU PCI init > (IOMMU_PCI_INIT stage). And for that reason snp_rmptable_init() is > currently invoked via device_initcall() and cannot be invoked via > subsys_initcall() as core IOMMU subsystem gets initialized via > subsys_initcall(). > > Now, if kvm_amd module is built-in, it gets initialized before SNP host > support is enabled in snp_rmptable_init() : > > [ 10.131811] kvm_amd: TSC scaling supported > [ 10.136384] kvm_amd: Nested Virtualization enabled > [ 10.141734] kvm_amd: Nested Paging enabled > [ 10.146304] kvm_amd: LBR virtualization supported > [ 10.151557] kvm_amd: SEV enabled (ASIDs 100 - 509) > [ 10.156905] kvm_amd: SEV-ES enabled (ASIDs 1 - 99) > [ 10.162256] kvm_amd: SEV-SNP enabled (ASIDs 1 - 99) > [ 10.171508] kvm_amd: Virtual VMLOAD VMSAVE supported > [ 10.177052] kvm_amd: Virtual GIF supported > ... > ... > [ 10.201648] kvm_amd: in svm_enable_virtualization_cpu > > And then svm_x86_ops->enable_virtualization_cpu() > (svm_enable_virtualization_cpu) programs MSR_VM_HSAVE_PA as following: > wrmsrl(MSR_VM_HSAVE_PA, sd->save_area_pa); > > So VM_HSAVE_PA is non-zero before SNP support is enabled on all CPUs. > > snp_rmptable_init() gets invoked after svm_enable_virtualization_cpu() > as following : > ... > [ 11.256138] kvm_amd: in svm_enable_virtualization_cpu > ... > [ 11.264918] SEV-SNP: in snp_rmptable_init > > This triggers a #GP exception in snp_rmptable_init() when snp_enable() > is invoked to set SNP_EN in SYSCFG MSR: > > [ 11.294289] unchecked MSR access error: WRMSR to 0xc0010010 (tried to write 0x0000000003fc0000) at rIP: 0xffffffffaf5d5c28 (native_write_msr+0x8/0x30) > ... > [ 11.294404] Call Trace: > [ 11.294482] <IRQ> > [ 11.294513] ? show_stack_regs+0x26/0x30 > [ 11.294522] ? ex_handler_msr+0x10f/0x180 > [ 11.294529] ? search_extable+0x2b/0x40 > [ 11.294538] ? fixup_exception+0x2dd/0x340 > [ 11.294542] ? exc_general_protection+0x14f/0x440 > [ 11.294550] ? asm_exc_general_protection+0x2b/0x30 > [ 11.294557] ? __pfx_snp_enable+0x10/0x10 > [ 11.294567] ? native_write_msr+0x8/0x30 > [ 11.294570] ? __snp_enable+0x5d/0x70 > [ 11.294575] snp_enable+0x19/0x20 > [ 11.294578] __flush_smp_call_function_queue+0x9c/0x3a0 > [ 11.294586] generic_smp_call_function_single_interrupt+0x17/0x20 > [ 11.294589] __sysvec_call_function+0x20/0x90 > [ 11.294596] sysvec_call_function+0x80/0xb0 > [ 11.294601] </IRQ> > [ 11.294603] <TASK> > [ 11.294605] asm_sysvec_call_function+0x1f/0x30 > ... > [ 11.294631] arch_cpu_idle+0xd/0x20 > [ 11.294633] default_idle_call+0x34/0xd0 > [ 11.294636] do_idle+0x1f1/0x230 > [ 11.294643] ? complete+0x71/0x80 > [ 11.294649] cpu_startup_entry+0x30/0x40 > [ 11.294652] start_secondary+0x12d/0x160 > [ 11.294655] common_startup_64+0x13e/0x141 > [ 11.294662] </TASK> > > This #GP exception is getting triggered due to the following errata for > AMD family 19h Models 10h-1Fh Processors: > > Processor may generate spurious #GP(0) Exception on WRMSR instruction: > Description: > The Processor will generate a spurious #GP(0) Exception on a WRMSR > instruction if the following conditions are all met: > - the target of the WRMSR is a SYSCFG register. > - the write changes the value of SYSCFG.SNPEn from 0 to 1. > - One of the threads that share the physical core has a non-zero > value in the VM_HSAVE_PA MSR. > > The document being referred to above: > https://www.amd.com/content/dam/amd/en/documents/processor-tech-docs/revision-guides/57095-PUB_1_01.pdf > > To summarize, with kvm_amd module being built-in, KVM/SVM initialization > happens before host SNP is enabled and this SVM initialization > sets VM_HSAVE_PA to non-zero, which then triggers a #GP when > SYSCFG.SNPEn is being set and this will subsequently cause > SNP_INIT(_EX) to fail with INVALID_CONFIG error as SYSCFG[SnpEn] is not > set on all CPUs. > > Essentially SNP host enabling code should be invoked before KVM > initialization, which is currently not the case when KVM is built-in. > > Add fix to call snp_rmptable_init() early from iommu_snp_enable() > directly and not invoked via device_initcall() which enables SNP host > support before KVM initialization with kvm_amd module built-in. > > Add additional handling for `iommu=off` or `amd_iommu=off` options. > > Note that IOMMUs need to be enabled for SNP initialization, therefore, > if host SNP support is enabled but late IOMMU initialization fails > then that will cause PSP driver's SNP_INIT to fail as IOMMU SNP sanity > checks in SNP firmware will fail with invalid configuration error as > below: > > [ 9.723114] ccp 0000:23:00.1: sev enabled > [ 9.727602] ccp 0000:23:00.1: psp enabled > [ 9.732527] ccp 0000:a2:00.1: enabling device (0000 -> 0002) > [ 9.739098] ccp 0000:a2:00.1: no command queues available > [ 9.745167] ccp 0000:a2:00.1: psp enabled > [ 9.805337] ccp 0000:23:00.1: SEV-SNP: failed to INIT rc -5, error 0x3 > [ 9.866426] ccp 0000:23:00.1: SEV API:1.53 build:5 > > Fixes: c3b86e61b756 ("x86/cpufeatures: Enable/unmask SEV-SNP CPU feature") > Co-developed-by: Sean Christopherson <seanjc@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > Co-developed-by: Vasant Hegde <vasant.hegde@amd.com> > Signed-off-by: Vasant Hegde <vasant.hegde@amd.com> > Cc: <Stable@vger.kernel.org> > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> > --- > arch/x86/include/asm/sev.h | 2 ++ > arch/x86/virt/svm/sev.c | 23 +++++++---------------- > drivers/iommu/amd/init.c | 34 ++++++++++++++++++++++++++++++---- > 3 files changed, 39 insertions(+), 20 deletions(-) For the IOMMU part: Acked-by: Joerg Roedel <jroedel@suse.de>
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 5d9685f92e5c..1581246491b5 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -531,6 +531,7 @@ static inline void __init snp_secure_tsc_init(void) { } #ifdef CONFIG_KVM_AMD_SEV bool snp_probe_rmptable_info(void); +int snp_rmptable_init(void); int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level); void snp_dump_hva_rmpentry(unsigned long address); int psmash(u64 pfn); @@ -541,6 +542,7 @@ void kdump_sev_callback(void); void snp_fixup_e820_tables(void); #else static inline bool snp_probe_rmptable_info(void) { return false; } +static inline int snp_rmptable_init(void) { return -ENOSYS; } static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; } static inline void snp_dump_hva_rmpentry(unsigned long address) {} static inline int psmash(u64 pfn) { return -ENODEV; } diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c index 1dcc027ec77e..42e74a5a7d78 100644 --- a/arch/x86/virt/svm/sev.c +++ b/arch/x86/virt/svm/sev.c @@ -505,19 +505,19 @@ static bool __init setup_rmptable(void) * described in the SNP_INIT_EX firmware command description in the SNP * firmware ABI spec. */ -static int __init snp_rmptable_init(void) +int __init snp_rmptable_init(void) { unsigned int i; u64 val; - if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP)) - return 0; + if (WARN_ON_ONCE(!cc_platform_has(CC_ATTR_HOST_SEV_SNP))) + return -ENOSYS; - if (!amd_iommu_snp_en) - goto nosnp; + if (WARN_ON_ONCE(!amd_iommu_snp_en)) + return -ENOSYS; if (!setup_rmptable()) - goto nosnp; + return -ENOSYS; /* * Check if SEV-SNP is already enabled, this can happen in case of @@ -530,7 +530,7 @@ static int __init snp_rmptable_init(void) /* Zero out the RMP bookkeeping area */ if (!clear_rmptable_bookkeeping()) { free_rmp_segment_table(); - goto nosnp; + return -ENOSYS; } /* Zero out the RMP entries */ @@ -562,17 +562,8 @@ static int __init snp_rmptable_init(void) crash_kexec_post_notifiers = true; return 0; - -nosnp: - cc_platform_clear(CC_ATTR_HOST_SEV_SNP); - return -ENOSYS; } -/* - * This must be called after the IOMMU has been initialized. - */ -device_initcall(snp_rmptable_init); - static void set_rmp_segment_info(unsigned int segment_shift) { rmp_segment_shift = segment_shift; diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c index c5cd92edada0..2fecfed75e54 100644 --- a/drivers/iommu/amd/init.c +++ b/drivers/iommu/amd/init.c @@ -3194,7 +3194,7 @@ static bool __init detect_ivrs(void) return true; } -static void iommu_snp_enable(void) +static __init void iommu_snp_enable(void) { #ifdef CONFIG_KVM_AMD_SEV if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP)) @@ -3219,6 +3219,14 @@ static void iommu_snp_enable(void) goto disable_snp; } + /* + * Enable host SNP support once SNP support is checked on IOMMU. + */ + if (snp_rmptable_init()) { + pr_warn("SNP: RMP initialization failed, SNP cannot be supported.\n"); + goto disable_snp; + } + pr_info("IOMMU SNP support enabled.\n"); return; @@ -3318,6 +3326,19 @@ static int __init iommu_go_to_state(enum iommu_init_state state) ret = state_next(); } + /* + * SNP platform initilazation requires IOMMUs to be fully configured. + * If the SNP support on IOMMUs has NOT been checked, simply mark SNP + * as unsupported. If the SNP support on IOMMUs has been checked and + * host SNP support enabled but RMP enforcement has not been enabled + * in IOMMUs, then the system is in a half-baked state, but can limp + * along as all memory should be Hypervisor-Owned in the RMP. WARN, + * but leave SNP as "supported" to avoid confusing the kernel. + */ + if (ret && cc_platform_has(CC_ATTR_HOST_SEV_SNP) && + !WARN_ON_ONCE(amd_iommu_snp_en)) + cc_platform_clear(CC_ATTR_HOST_SEV_SNP); + return ret; } @@ -3426,18 +3447,23 @@ void __init amd_iommu_detect(void) int ret; if (no_iommu || (iommu_detected && !gart_iommu_aperture)) - return; + goto disable_snp; if (!amd_iommu_sme_check()) - return; + goto disable_snp; ret = iommu_go_to_state(IOMMU_IVRS_DETECTED); if (ret) - return; + goto disable_snp; amd_iommu_detected = true; iommu_detected = 1; x86_init.iommu.iommu_init = amd_iommu_init; + return; + +disable_snp: + if (cc_platform_has(CC_ATTR_HOST_SEV_SNP)) + cc_platform_clear(CC_ATTR_HOST_SEV_SNP); } /****************************************************************************