Re: [RFC PATCH 3/12] x86/HV: Initialize GHCB page and shared memory boundary

[Vitaly Kuznetsov]

Tianyu Lan <ltykernel@xxxxxxxxx> writes:

> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
>
> Hyper-V exposes GHCB page via SEV ES GHCB MSR for SNP guest
> to communicate with hypervisor. Map GHCB page for all
> cpus to read/write MSR register and submit hvcall request
> via GHCB. Hyper-V also exposes shared memory boundary via
> cpuid HYPERV_CPUID_ISOLATION_CONFIG and store it in the
> shared_gpa_boundary of ms_hyperv struct. This prepares
> to share memory with host for SNP guest.
>

It seems the patch could be split into two: per-cpu GHCB setup and
shared memory boundary setup as these changes seem to be independent.

> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
>  arch/x86/hyperv/hv_init.c      | 52 +++++++++++++++++++++++++++++++---
>  arch/x86/kernel/cpu/mshyperv.c |  2 ++
>  include/asm-generic/mshyperv.h | 14 ++++++++-
>  3 files changed, 63 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 0db5137d5b81..90e65fbf4c58 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -82,6 +82,9 @@ static int hv_cpu_init(unsigned int cpu)
>  	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
>  	void **input_arg;
>  	struct page *pg;
> +	u64 ghcb_gpa;
> +	void *ghcb_va;
> +	void **ghcb_base;
>  
>  	/* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
>  	pg = alloc_pages(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, hv_root_partition ? 1 : 0);
> @@ -128,6 +131,17 @@ static int hv_cpu_init(unsigned int cpu)
>  		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
>  	}
>  
> +	if (ms_hyperv.ghcb_base) {
> +		rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +
> +		ghcb_va = ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);

Do we actually need to do ioremap_cache() and not ioremap_uc() for GHCB?
(just wondering)

> +		if (!ghcb_va)
> +			return -ENOMEM;
> +
> +		ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> +		*ghcb_base = ghcb_va;
> +	}
> +
>  	return 0;
>  }
>  
> @@ -223,6 +237,7 @@ static int hv_cpu_die(unsigned int cpu)
>  	unsigned long flags;
>  	void **input_arg;
>  	void *pg;
> +	void **ghcb_va = NULL;
>  
>  	local_irq_save(flags);
>  	input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> @@ -236,6 +251,13 @@ static int hv_cpu_die(unsigned int cpu)
>  		*output_arg = NULL;
>  	}
>  
> +	if (ms_hyperv.ghcb_base) {
> +		ghcb_va = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> +		if (*ghcb_va)
> +			iounmap(*ghcb_va);
> +		*ghcb_va = NULL;
> +	}
> +
>  	local_irq_restore(flags);
>  
>  	free_pages((unsigned long)pg, hv_root_partition ? 1 : 0);
> @@ -372,6 +394,9 @@ void __init hyperv_init(void)
>  	u64 guest_id, required_msrs;
>  	union hv_x64_msr_hypercall_contents hypercall_msr;
>  	int cpuhp, i;
> +	u64 ghcb_gpa;
> +	void *ghcb_va;
> +	void **ghcb_base;
>  
>  	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
>  		return;
> @@ -432,9 +457,24 @@ void __init hyperv_init(void)
>  			VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX,
>  			VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
>  			__builtin_return_address(0));
> -	if (hv_hypercall_pg == NULL) {
> -		wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
> -		goto remove_cpuhp_state;
> +	if (hv_hypercall_pg == NULL)
> +		goto clean_guest_os_id;
> +
> +	if (hv_isolation_type_snp()) {
> +		ms_hyperv.ghcb_base = alloc_percpu(void *);
> +		if (!ms_hyperv.ghcb_base)
> +			goto clean_guest_os_id;
> +
> +		rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +		ghcb_va = ioremap_cache(ghcb_gpa, HV_HYP_PAGE_SIZE);
> +		if (!ghcb_va) {
> +			free_percpu(ms_hyperv.ghcb_base);
> +			ms_hyperv.ghcb_base = NULL;
> +			goto clean_guest_os_id;
> +		}
> +
> +		ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
> +		*ghcb_base = ghcb_va;
>  	}
>  
>  	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> @@ -499,7 +539,8 @@ void __init hyperv_init(void)
>  
>  	return;
>  
> -remove_cpuhp_state:
> +clean_guest_os_id:
> +	wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
>  	cpuhp_remove_state(cpuhp);
>  free_vp_assist_page:
>  	kfree(hv_vp_assist_page);
> @@ -528,6 +569,9 @@ void hyperv_cleanup(void)
>  	 */
>  	hv_hypercall_pg = NULL;
>  
> +	if (ms_hyperv.ghcb_base)
> +		free_percpu(ms_hyperv.ghcb_base);
> +
>  	/* Reset the hypercall page */
>  	hypercall_msr.as_uint64 = 0;
>  	wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 347c32eac8fd..d6c363456cbf 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -330,6 +330,8 @@ static void __init ms_hyperv_init_platform(void)
>  	if (ms_hyperv.features_b & HV_ISOLATION) {
>  		ms_hyperv.isolation_config_a = cpuid_eax(HYPERV_CPUID_ISOLATION_CONFIG);
>  		ms_hyperv.isolation_config_b = cpuid_ebx(HYPERV_CPUID_ISOLATION_CONFIG);
> +		ms_hyperv.shared_gpa_boundary =
> +			(u64)1 << ms_hyperv.shared_gpa_boundary_bits;
>  
>  		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
>  			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
> index dff58a3db5d5..ad0e33776668 100644
> --- a/include/asm-generic/mshyperv.h
> +++ b/include/asm-generic/mshyperv.h
> @@ -34,7 +34,19 @@ struct ms_hyperv_info {
>  	u32 max_vp_index;
>  	u32 max_lp_index;
>  	u32 isolation_config_a;
> -	u32 isolation_config_b;
> +	union
> +	{
> +		u32 isolation_config_b;;
> +		struct {
> +			u32 cvm_type : 4;
> +			u32 Reserved11 : 1;
> +			u32 shared_gpa_boundary_active : 1;
> +			u32 shared_gpa_boundary_bits : 6;
> +			u32 Reserved12 : 20;
> +		};
> +	};
> +	void  __percpu **ghcb_base;
> +	u64 shared_gpa_boundary;
>  };
>  extern struct ms_hyperv_info ms_hyperv;

-- 
Vitaly