On Wed, Dec 14, 2022 at 01:40:06PM -0600, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@xxxxxxx>
>
> The memory integrity guarantees of SEV-SNP are enforced through a new
> structure called the Reverse Map Table (RMP). The RMP is a single data
> structure shared across the system that contains one entry for every 4K
> page of DRAM that may be used by SEV-SNP VMs. The goal of RMP is to
> track the owner of each page of memory. Pages of memory can be owned by
> the hypervisor, owned by a specific VM or owned by the AMD-SP. See APM2
> section 15.36.3 for more detail on RMP.
>
> The RMP table is used to enforce access control to memory. The table itself
> is not directly writable by the software. New CPU instructions (RMPUPDATE,
> PVALIDATE, RMPADJUST) are used to manipulate the RMP entries.
>
> Based on the platform configuration, the BIOS reserves the memory used
> for the RMP table. The start and end address of the RMP table must be
> queried by reading the RMP_BASE and RMP_END MSRs. If the RMP_BASE and
> RMP_END are not set then disable the SEV-SNP feature.
>
> The SEV-SNP feature is enabled only after the RMP table is successfully
> initialized.
>
> Also set SYSCFG.MFMD when enabling SNP as SEV-SNP FW >= 1.51 requires
> that SYSCFG.MFMD must be se
set.
>
> RMP table entry format is non-architectural and it can vary by processor
> and is defined by the PPR. Restrict SNP support on the known CPU model
> and family for which the RMP table entry format is currently defined for.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
> Signed-off-b: Ashish Kalra <ashish.kalra@xxxxxxx>
^^
Somebody ate a 'y' here. :)
> Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
> ---
> arch/x86/include/asm/disabled-features.h | 8 +-
> arch/x86/include/asm/msr-index.h | 11 +-
> arch/x86/kernel/sev.c | 180 +++++++++++++++++++++++
> 3 files changed, 197 insertions(+), 2 deletions(-)
...
> +static __init int __snp_rmptable_init(void)
Why is this one carved out of snp_rmptable_init() ?
> +{
> + u64 rmp_base, sz;
> + void *start;
> + u64 val;
> +
> + if (!get_rmptable_info(&rmp_base, &sz))
> + return 1;
> +
> + start = memremap(rmp_base, sz, MEMREMAP_WB);
> + if (!start) {
> + pr_err("Failed to map RMP table addr 0x%llx size 0x%llx\n", rmp_base, sz);
> + return 1;
> + }
> +
> + /*
> + * Check if SEV-SNP is already enabled, this can happen in case of
> + * kexec boot.
> + */
> + rdmsrl(MSR_AMD64_SYSCFG, val);
> + if (val & MSR_AMD64_SYSCFG_SNP_EN)
> + goto skip_enable;
> +
> + /* Initialize the RMP table to zero */
Useless comment.
> + memset(start, 0, sz);
> +
> + /* Flush the caches to ensure that data is written before SNP is enabled. */
> + wbinvd_on_all_cpus();
> +
> + /* MFDM must be enabled on all the CPUs prior to enabling SNP. */
> + on_each_cpu(mfd_enable, NULL, 1);
> +
> + /* Enable SNP on all CPUs. */
> + on_each_cpu(snp_enable, NULL, 1);
What happens if someone boots the machine with maxcpus=N, where N is
less than all CPUs on the machine? The hotplug notifier should handle it
but have you checked that it works fine?
> +skip_enable:
> + rmptable_start = (unsigned long)start;
> + rmptable_end = rmptable_start + sz - 1;
> +
> + return 0;
> +}
> +
> +static int __init snp_rmptable_init(void)
> +{
> + int family, model;
> +
> + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> + return 0;
> +
> + family = boot_cpu_data.x86;
> + model = boot_cpu_data.x86_model;
Looks useless - just use boot_cpu_data directly below.
> +
> + /*
> + * RMP table entry format is not architectural and it can vary by processor and
> + * is defined by the per-processor PPR. Restrict SNP support on the known CPU
> + * model and family for which the RMP table entry format is currently defined for.
> + */
> + if (family != 0x19 || model > 0xaf)
> + goto nosnp;
> +
> + if (amd_iommu_snp_enable())
> + goto nosnp;
> +
> + if (__snp_rmptable_init())
> + goto nosnp;
> +
> + cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/rmptable_init:online", __snp_enable, NULL);
> +
> + return 0;
> +
> +nosnp:
> + setup_clear_cpu_cap(X86_FEATURE_SEV_SNP);
> + return -ENOSYS;
> +}
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
