LKML: Tom Lendacky: Re: [PATCH 1/5] KVM: SVM: Decrypt SEV VMSA in dump

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Update the dump_vmcb() routine to output >> some of the SEV VMSA contents if possible. This can be useful for >> debug purposes. >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> --- >> + /* >> + * Return the target page to a hypervisor page no matter what. >> + * If this fails, the page can't be used, so leak it and don't >> + * try to use it. >> + */ >> + if (snp_page_reclaim(vcpu->kvm, PHYS_PFN(__pa(vmsa)))) >> + return NULL; > > And actually I should call snp_leak_pages() here to record that. I'll add > that to the next version. Err... snp_page_reclaim() already does that. Nevermind. Thanks, Tom > > Thanks, > Tom > >> + >> + if (ret) { >> + pr_err("SEV: SNP_DBG_DECRYPT failed ret=%d, fw_error=%d (%#x)\n", >> + ret, error, error); >> + free_page((unsigned long)vmsa); >> + >> + return NULL; >> + } >> + } else { >> + struct sev_data_dbg dbg = {0}; >> + struct page *vmsa_page; >> + >> + vmsa_page = alloc_page(GFP_KERNEL); >> + if (!vmsa_page) >> + return NULL; >> + >> + vmsa = page_address(vmsa_page); >> + >> + dbg.handle = sev->handle; >> + dbg.src_addr = svm->vmcb->control.vmsa_pa; >> + dbg.dst_addr = __psp_pa(vmsa); >> + dbg.len = PAGE_SIZE; >> + >> + ret = sev_issue_cmd(vcpu->kvm, SEV_CMD_DBG_DECRYPT, &dbg, &error); >> + if (ret) { >> + pr_err("SEV: SEV_CMD_DBG_DECRYPT failed ret=%d, fw_error=%d (0x%x)\n", >> + ret, error, error); >> + __free_page(vmsa_page); >> + >> + return NULL; >> + } >> + } >> + >> + return vmsa; >> +} >> + >> +void sev_free_decrypted_vmsa(struct kvm_vcpu *vcpu, struct vmcb_save_area *vmsa) >> +{ >> + /* If the VMSA has not yet been encrypted, nothing was allocated */ >> + if (!vcpu->arch.guest_state_protected || !vmsa) >> + return; >> + >> + free_page((unsigned long)vmsa); >> +} >> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >> index e67de787fc71..21477871073c 100644 >> --- a/arch/x86/kvm/svm/svm.c >> +++ b/arch/x86/kvm/svm/svm.c >> @@ -3423,6 +3423,15 @@ static void dump_vmcb(struct kvm_vcpu *vcpu) >> pr_err("%-20s%016llx\n", "avic_logical_id:", control->avic_logical_id); >> pr_err("%-20s%016llx\n", "avic_physical_id:", control->avic_physical_id); >> pr_err("%-20s%016llx\n", "vmsa_pa:", control->vmsa_pa); >> + >> + if (sev_es_guest(vcpu->kvm)) { >> + save = sev_decrypt_vmsa(vcpu); >> + if (!save) >> + goto no_vmsa; >> + >> + save01 = save; >> + } >> + >> pr_err("VMCB State Save Area:\n"); >> pr_err("%-5s s: %04x a: %04x l: %08x b: %016llx\n", >> "es:", >> @@ -3493,6 +3502,10 @@ static void dump_vmcb(struct kvm_vcpu *vcpu) >> pr_err("%-15s %016llx %-13s %016llx\n", >> "excp_from:", save->last_excp_from, >> "excp_to:", save->last_excp_to); >> + >> +no_vmsa: >> + if (sev_es_guest(vcpu->kvm)) >> + sev_free_decrypted_vmsa(vcpu, save); >> } >> >> static bool svm_check_exit_valid(u64 exit_code) >> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h >> index ea44c1da5a7c..66979ddc3659 100644 >> --- a/arch/x86/kvm/svm/svm.h >> +++ b/arch/x86/kvm/svm/svm.h >> @@ -98,6 +98,7 @@ struct kvm_sev_info { >> unsigned int asid; /* ASID used for this guest */ >> unsigned int handle; /* SEV firmware handle */ >> int fd; /* SEV device fd */ >> + unsigned long policy; >> unsigned long pages_locked; /* Number of pages locked */ >> struct list_head regions_list; /* List of registered regions */ >> u64 ap_jump_table; /* SEV-ES AP Jump Table address */ >> @@ -114,6 +115,9 @@ struct kvm_sev_info { >> struct mutex guest_req_mutex; /* Must acquire before using bounce buffers */ >> }; >> >> +#define SEV_POLICY_NODBG BIT_ULL(0) >> +#define SNP_POLICY_DEBUG BIT_ULL(19) >> + >> struct kvm_svm { >> struct kvm kvm; >> >> @@ -756,6 +760,8 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu); >> int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order); >> void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end); >> int sev_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn); >> +struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu); >> +void sev_free_decrypted_vmsa(struct kvm_vcpu *vcpu, struct vmcb_save_area *vmsa); >> #else >> static inline struct page *snp_safe_alloc_page_node(int node, gfp_t gfp) >> { >> @@ -787,6 +793,11 @@ static inline int sev_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn) >> return 0; >> } >> >> +static inline struct vmcb_save_area *sev_decrypt_vmsa(struct kvm_vcpu *vcpu) >> +{ >> + return NULL; >> +} >> +static inline void sev_free_decrypted_vmsa(struct kvm_vcpu *vcpu, struct vmcb_save_area *vmsa) {} >> #endif >> >> /* vmenter.S */ </pre></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerr.gif" width="32" height="32" alt="\" /></td></tr><tr><td align="right" valign="bottom"> 聽 </td></tr><tr><td align="right" valign="bottom">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerl.gif" width="32" height="32" alt="\" /></td><td class="c">聽</td><td class="c" valign="bottom" style="padding-bottom: 0px"><img src="/images/bcornerr.gif" width="32" height="32" alt="/" /></td></tr><tr><td align="right" valign="top" colspan="2"> 聽 </td><td class="lm">Last update: 2025-03-21 15:42 聽聽 [W:0.086 / U:1.970 seconds] 漏2003-2020 <a href="http://blog.jasper.es/">Jasper Spaans</a>|hosted at <a href="https://www.digitalocean.com/?refcode=9a8e99d24cf9">Digital Ocean</a> and my Meterkast|<a href="http://blog.jasper.es/categories.html#lkml-ref">Read the blog</a></td><td>聽</td></tr></table><script language="javascript" src="/js/styleswitcher.js" type="text/javascript"></script></body></html>

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LKML: Tom Lendacky: Re: [PATCH 1/5] KVM: SVM: Decrypt SEV VMSA in dump_vmcb() if debugging is enabled