[PATCH Part1 RFC v4 11/36] x86/sev: Register GHCB memory when SEV-SNP is active
From: Brijesh Singh <hidden>
Date: 2021-07-07 18:16:32
Also in:
kvm, linux-crypto, linux-efi, linux-mm, lkml, platform-driver-x86
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
The SEV-SNP guest is required to perform GHCB GPA registration. This is because the hypervisor may prefer that a guest use a consistent and/or specific GPA for the GHCB associated with a vCPU. For more information, see the GHCB specification section GHCB GPA Registration. During the boot, init_ghcb() allocates a per-cpu GHCB page. On very first VC exception, the exception handler switch to using the per-cpu GHCB page allocated during the init_ghcb(). The GHCB page must be registered in the current vcpu context. Signed-off-by: Brijesh Singh <redacted> --- arch/x86/kernel/sev-internal.h | 12 ++++++++++++ arch/x86/kernel/sev.c | 29 +++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) create mode 100644 arch/x86/kernel/sev-internal.h
diff --git a/arch/x86/kernel/sev-internal.h b/arch/x86/kernel/sev-internal.h
new file mode 100644
index 000000000000..0fb7324803b4
--- /dev/null
+++ b/arch/x86/kernel/sev-internal.h@@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Forward declarations for sev-shared.c + * + * Author: Brijesh Singh <brijesh.singh@amd.com> + */ + +#ifndef __X86_SEV_INTERNAL_H__ + +static void snp_register_ghcb_early(unsigned long paddr); + +#endif /* __X86_SEV_INTERNAL_H__ */
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 504169f1966b..c7ff60b55bde 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c@@ -31,6 +31,8 @@ #include <asm/smp.h> #include <asm/cpu.h> +#include "sev-internal.h" + #define DR7_RESET_VALUE 0x400 /* For early boot hypervisor communication in SEV-ES enabled guests */
@@ -87,6 +89,13 @@ struct sev_es_runtime_data { * is currently unsupported in SEV-ES guests. */ unsigned long dr7; + + /* + * SEV-SNP requires that the GHCB must be registered before using it. + * The flag below will indicate whether the GHCB is registered, if its + * not registered then sev_es_get_ghcb() will perform the registration. + */ + bool snp_ghcb_registered; }; struct ghcb_state {
@@ -194,6 +203,17 @@ void noinstr __sev_es_ist_exit(void) this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist); } +static void snp_register_ghcb(struct sev_es_runtime_data *data, unsigned long paddr) +{ + if (data->snp_ghcb_registered) + return; + + snp_register_ghcb_early(paddr); + + data->snp_ghcb_registered = true; +} + + /* * Nothing shall interrupt this code path while holding the per-CPU * GHCB. The backup GHCB is only for NMIs interrupting this path.
@@ -240,6 +260,10 @@ static noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state) data->ghcb_active = true; } + /* SEV-SNP guest requires that GHCB must be registered. */ + if (sev_feature_enabled(SEV_SNP)) + snp_register_ghcb(data, __pa(ghcb)); + return ghcb; }
@@ -684,6 +708,10 @@ static bool __init setup_ghcb(void) /* Alright - Make the boot-ghcb public */ boot_ghcb = &boot_ghcb_page; + /* SEV-SNP guest requires that GHCB GPA must be registered. */ + if (sev_feature_enabled(SEV_SNP)) + snp_register_ghcb_early(__pa(&boot_ghcb_page)); + return true; }
@@ -773,6 +801,7 @@ static void __init init_ghcb(int cpu) data->ghcb_active = false; data->backup_ghcb_active = false; + data->snp_ghcb_registered = false; } void __init sev_es_init_vc_handling(void)
--
2.17.1