[01/13] x86/HV: Initialize GHCB page in Isolation VM

Commit Message

Tianyu Lan July 28, 2021, 2:52 p.m. UTC

From: Tianyu Lan <[e-mail]>

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.

Signed-off-by: Tianyu Lan <[e-mail]>
---
 arch/x86/hyperv/hv_init.c       | 73 +++++++++++++++++++++++++++++++--
 arch/x86/include/asm/mshyperv.h |  2 +
 include/asm-generic/mshyperv.h  |  2 +
 3 files changed, 73 insertions(+), 4 deletions(-)

Comments

Joerg Roedel Aug. 2, 2021, 11:53 a.m. UTC | #1

On Wed, Jul 28, 2021 at 10:52:16AM -0400, Tianyu Lan wrote:
> +static int hyperv_init_ghcb(void)
> +{
> +	u64 ghcb_gpa;
> +	void *ghcb_va;
> +	void **ghcb_base;
> +
> +	if (!ms_hyperv.ghcb_base)
> +		return -EINVAL;
> +
> +	rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
> +	ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);

This deserves a comment. As I understand it, the GHCB pa is set by
Hyper-V or the paravisor, so the page does not need to be allocated by
Linux.
And it is not mapped unencrypted because the GHCB page is allocated
above the VTOM boundary?

> @@ -167,6 +190,31 @@ static int hv_cpu_die(unsigned int cpu)
>  {
>  	struct hv_reenlightenment_control re_ctrl;
>  	unsigned int new_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);
> +	pg = *input_arg;

Pg is never used later on, why is it set?

Tianyu Lan Aug. 2, 2021, 12:35 p.m. UTC | #2

Hi Joerg:
      Thanks for your review.


On 8/2/2021 7:53 PM, Joerg Roedel wrote:
> On Wed, Jul 28, 2021 at 10:52:16AM -0400, Tianyu Lan wrote:
>> +static int hyperv_init_ghcb(void)
>> +{
>> +	u64 ghcb_gpa;
>> +	void *ghcb_va;
>> +	void **ghcb_base;
>> +
>> +	if (!ms_hyperv.ghcb_base)
>> +		return -EINVAL;
>> +
>> +	rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
>> +	ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
> 
> This deserves a comment. As I understand it, the GHCB pa is set by
> Hyper-V or the paravisor, so the page does not need to be allocated by
> Linux.
> And it is not mapped unencrypted because the GHCB page is allocated
> above the VTOM boundary?

You are right. The ghdb page is allocated by paravisor and its physical 
address is above VTOM boundary. Will add a comment to describe this.
Thanks for suggestion.

> 
>> @@ -167,6 +190,31 @@ static int hv_cpu_die(unsigned int cpu)
>>   {
>>   	struct hv_reenlightenment_control re_ctrl;
>>   	unsigned int new_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);
>> +	pg = *input_arg;
> 
> Pg is never used later on, why is it set?

Sorry for noise. This should be removed during rebase and will fix in 
the next version.

Patch

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 4a643a85d570..ee449c076ef4 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -20,6 +20,7 @@ 
 #include <linux/kexec.h>
 #include <linux/version.h>
 #include <linux/vmalloc.h>
+#include <linux/io.h>
 #include <linux/mm.h>
 #include <linux/hyperv.h>
 #include <linux/slab.h>
@@ -42,6 +43,26 @@  static void *hv_hypercall_pg_saved;
 struct hv_vp_assist_page **hv_vp_assist_page;
 EXPORT_SYMBOL_GPL(hv_vp_assist_page);
 
+static int hyperv_init_ghcb(void)
+{
+	u64 ghcb_gpa;
+	void *ghcb_va;
+	void **ghcb_base;
+
+	if (!ms_hyperv.ghcb_base)
+		return -EINVAL;
+
+	rdmsrl(MSR_AMD64_SEV_ES_GHCB, ghcb_gpa);
+	ghcb_va = memremap(ghcb_gpa, HV_HYP_PAGE_SIZE, MEMREMAP_WB);
+	if (!ghcb_va)
+		return -ENOMEM;
+
+	ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
+	*ghcb_base = ghcb_va;
+
+	return 0;
+}
+
 static int hv_cpu_init(unsigned int cpu)
 {
 	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
@@ -75,6 +96,8 @@  static int hv_cpu_init(unsigned int cpu)
 		wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
 	}
 
+	hyperv_init_ghcb();
+
 	return 0;
 }
 
@@ -167,6 +190,31 @@  static int hv_cpu_die(unsigned int cpu)
 {
 	struct hv_reenlightenment_control re_ctrl;
 	unsigned int new_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);
+	pg = *input_arg;
+	*input_arg = NULL;
+
+	if (hv_root_partition) {
+		void **output_arg;
+
+		output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
+		*output_arg = NULL;
+	}
+
+	if (ms_hyperv.ghcb_base) {
+		ghcb_va = (void **)this_cpu_ptr(ms_hyperv.ghcb_base);
+		if (*ghcb_va)
+			memunmap(*ghcb_va);
+		*ghcb_va = NULL;
+	}
+
+	local_irq_restore(flags);
 
 	hv_common_cpu_die(cpu);
 
@@ -340,9 +388,22 @@  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;
+
+		if (hyperv_init_ghcb()) {
+			free_percpu(ms_hyperv.ghcb_base);
+			ms_hyperv.ghcb_base = NULL;
+			goto clean_guest_os_id;
+		}
+
+		/* Hyper-V requires to write guest os id via ghcb in SNP IVM. */
+		hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id);
 	}
 
 	rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
@@ -403,7 +464,8 @@  void __init hyperv_init(void)
 	hv_query_ext_cap(0);
 	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);
@@ -431,6 +493,9 @@  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/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index adccbc209169..6627cfd2bfba 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -11,6 +11,8 @@ 
 #include <asm/paravirt.h>
 #include <asm/mshyperv.h>
 
+DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
+
 typedef int (*hyperv_fill_flush_list_func)(
 		struct hv_guest_mapping_flush_list *flush,
 		void *data);
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index c1ab6a6e72b5..4269f3174e58 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -36,6 +36,7 @@  struct ms_hyperv_info {
 	u32 max_lp_index;
 	u32 isolation_config_a;
 	u32 isolation_config_b;
+	void  __percpu **ghcb_base;
 };
 extern struct ms_hyperv_info ms_hyperv;
 
@@ -237,6 +238,7 @@  bool hv_is_hyperv_initialized(void);
 bool hv_is_hibernation_supported(void);
 enum hv_isolation_type hv_get_isolation_type(void);
 bool hv_is_isolation_supported(void);
+bool hv_isolation_type_snp(void);
 void hyperv_cleanup(void);
 bool hv_query_ext_cap(u64 cap_query);
 #else /* CONFIG_HYPERV */