From: Jinank Jain <jinankjain@xxxxxxxxxxxxxxxxxxx> Sent: Tuesday, December 13, 2022 10:33 PM
>
> Child partitions are free to allocate SynIC message and event page but in
> case of root partition it must use the pages allocated by Microsoft
> Hypervisor (MSHV). Base address for these pages can be found using
> synthetic MSRs exposed by MSHV. There is a slight difference in those MSRs
> for nested vs non-nested root partition.
>
> Signed-off-by: Jinank Jain <jinankjain@xxxxxxxxxxxxxxxxxxx>
You have addressed all my previous comments and those areas
look good. But I see a new issue that I had not noticed before.
See comment below.
> ---
> arch/x86/include/asm/hyperv-tlfs.h | 11 +++++
> arch/x86/include/asm/mshyperv.h | 30 +++-----------
> arch/x86/kernel/cpu/mshyperv.c | 65 ++++++++++++++++++++++++++++++
> drivers/hv/hv.c | 19 ++++++---
> 4 files changed, 96 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 58c03d18c235..b5019becb618 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -225,6 +225,17 @@ enum hv_isolation_type {
> #define HV_REGISTER_SINT14 0x4000009E
> #define HV_REGISTER_SINT15 0x4000009F
>
> +/*
> + * Define synthetic interrupt controller model specific registers for
> + * nested hypervisor.
> + */
> +#define HV_REGISTER_NESTED_SCONTROL 0x40001080
> +#define HV_REGISTER_NESTED_SVERSION 0x40001081
> +#define HV_REGISTER_NESTED_SIEFP 0x40001082
> +#define HV_REGISTER_NESTED_SIMP 0x40001083
> +#define HV_REGISTER_NESTED_EOM 0x40001084
> +#define HV_REGISTER_NESTED_SINT0 0x40001090
> +
> /*
> * Synthetic Timer MSRs. Four timers per vcpu.
> */
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 61f0c206bff0..c38e4c66a3ac 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -198,30 +198,10 @@ static inline bool hv_is_synic_reg(unsigned int reg)
> return false;
> }
>
> -static inline u64 hv_get_register(unsigned int reg)
> -{
> - u64 value;
> -
> - if (hv_is_synic_reg(reg) && hv_isolation_type_snp())
> - hv_ghcb_msr_read(reg, &value);
> - else
> - rdmsrl(reg, value);
> - return value;
> -}
> -
> -static inline void hv_set_register(unsigned int reg, u64 value)
> -{
> - if (hv_is_synic_reg(reg) && hv_isolation_type_snp()) {
> - hv_ghcb_msr_write(reg, value);
> -
> - /* Write proxy bit via wrmsl instruction */
> - if (reg >= HV_REGISTER_SINT0 &&
> - reg <= HV_REGISTER_SINT15)
> - wrmsrl(reg, value | 1 << 20);
> - } else {
> - wrmsrl(reg, value);
> - }
> -}
> +u64 hv_get_register(unsigned int reg);
> +void hv_set_register(unsigned int reg, u64 value);
> +u64 hv_get_non_nested_register(unsigned int reg);
> +void hv_set_non_nested_register(unsigned int reg, u64 value);
>
> #else /* CONFIG_HYPERV */
> static inline void hyperv_init(void) {}
> @@ -241,6 +221,8 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
> }
> static inline void hv_set_register(unsigned int reg, u64 value) { }
> static inline u64 hv_get_register(unsigned int reg) { return 0; }
> +static inline void hv_set_non_nested_register(unsigned int reg, u64 value) { }
> +static inline u64 hv_get_non_nested_register(unsigned int reg) { return 0; }
> static inline int hv_set_mem_host_visibility(unsigned long addr, int numpages,
> bool visible)
> {
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index f9b78d4829e3..938fc82edf05 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -41,7 +41,72 @@ bool hv_root_partition;
> bool hv_nested;
> struct ms_hyperv_info ms_hyperv;
>
> +static inline unsigned int hv_get_nested_reg(unsigned int reg)
> +{
> + switch (reg) {
> + case HV_REGISTER_SIMP:
> + return HV_REGISTER_NESTED_SIMP;
> + case HV_REGISTER_SIEFP:
> + return HV_REGISTER_NESTED_SIEFP;
> + case HV_REGISTER_SVERSION:
> + return HV_REGISTER_NESTED_SVERSION;
> + case HV_REGISTER_SCONTROL:
> + return HV_REGISTER_NESTED_SCONTROL;
> + case HV_REGISTER_SINT0:
> + return HV_REGISTER_NESTED_SINT0;
> + case HV_REGISTER_EOM:
> + return HV_REGISTER_NESTED_EOM;
> + default:
> + return reg;
> + }
> +}
> +
> #if IS_ENABLED(CONFIG_HYPERV)
> +u64 hv_get_non_nested_register(unsigned int reg)
> +{
> + u64 value;
> +
> + if (hv_is_synic_reg(reg) && hv_isolation_type_snp())
> + hv_ghcb_msr_read(reg, &value);
> + else
> + rdmsrl(reg, value);
> + return value;
> +}
> +EXPORT_SYMBOL_GPL(hv_get_non_nested_register);
> +
> +void hv_set_non_nested_register(unsigned int reg, u64 value)
> +{
> + if (hv_is_synic_reg(reg) && hv_isolation_type_snp()) {
> + hv_ghcb_msr_write(reg, value);
> +
> + /* Write proxy bit via wrmsl instruction */
> + if (reg >= HV_REGISTER_SINT0 &&
> + reg <= HV_REGISTER_SINT15)
> + wrmsrl(reg, value | 1 << 20);
> + } else {
> + wrmsrl(reg, value);
> + }
> +}
> +EXPORT_SYMBOL_GPL(hv_set_non_nested_register);
> +
> +u64 hv_get_register(unsigned int reg)
> +{
> + if (hv_nested)
> + reg = hv_get_nested_reg(reg);
> +
> + return hv_get_non_nested_register(reg);
> +}
> +EXPORT_SYMBOL_GPL(hv_get_register);
> +
> +void hv_set_register(unsigned int reg, u64 value)
> +{
> + if (hv_nested)
> + reg = hv_get_nested_reg(reg);
> +
> + hv_set_non_nested_register(reg, value);
> +}
> +EXPORT_SYMBOL_GPL(hv_set_register);
> +
> static void (*vmbus_handler)(void);
> static void (*hv_stimer0_handler)(void);
> static void (*hv_kexec_handler)(void);
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 4d6480d57546..986814a903ee 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -147,7 +147,7 @@ int hv_synic_alloc(void)
> * Synic message and event pages are allocated by paravisor.
> * Skip these pages allocation here.
> */
> - if (!hv_isolation_type_snp()) {
> + if (!hv_isolation_type_snp() && !hv_root_partition) {
> hv_cpu->synic_message_page =
> (void *)get_zeroed_page(GFP_ATOMIC);
> if (hv_cpu->synic_message_page == NULL) {
> @@ -188,8 +188,16 @@ void hv_synic_free(void)
> struct hv_per_cpu_context *hv_cpu
> = per_cpu_ptr(hv_context.cpu_context, cpu);
>
> - free_page((unsigned long)hv_cpu->synic_event_page);
> - free_page((unsigned long)hv_cpu->synic_message_page);
> + if (hv_root_partition) {
> + if (hv_cpu->synic_event_page != NULL)
> + memunmap(hv_cpu->synic_event_page);
> +
> + if (hv_cpu->synic_message_page != NULL)
> + memunmap(hv_cpu->synic_message_page);
These memunmap() calls seem to be done in the wrong place. There are two
pairs of functions that should be symmetrical unless there's a really good
reason otherwise:
1. hv_synic_alloc() and hv_synic_free()
2. hv_synic_enable_regs() and hv_synic_disable_regs()
The functions in #1 handle the allocation and freeing of these three
pages: synic_event_page, synic_message_page, and post_msg_page.
If the synic_event_page and synic_message_page don't need to be
allocated because they are provided by the hypervisor or paravisor,
then the allocation is skipped in hv_synic_alloc(), and the free_page
operations in hv_synic_free() are no-ops if the corresponding pointer
is NULL.
The functions in #2 should handle the mapping and unmapping in the
case of pages provided by the hypervisor or paravisor. It appears
that the hv_isolation_type_snp() case does this (mostly) correctly.
But your code does the unmap in hv_synic_free(), which isn't
symmetrical. Unless there's something unique about the situation
when running in the root partition, the unmap should be done in
hv_synic_disable_regs() like it is for the SNP case.
My "mostly" correctly comment above is because the current code
in hv_synic_disable_regs() should be setting hv_cpu->synic_message_page
and hv_cpu->synic_event_page to NULL after the unmap is done.
Those pointers must be reverted to NULL so that if hv_synic_free() is
then run, it won't try to free pages that were provided by the hypervisor
or paravisor.
Michael
> + } else {
> + free_page((unsigned long)hv_cpu->synic_event_page);
> + free_page((unsigned long)hv_cpu->synic_message_page);
> + }
> free_page((unsigned long)hv_cpu->post_msg_page);
> }
>
> @@ -214,9 +222,10 @@ void hv_synic_enable_regs(unsigned int cpu)
>
> /* Setup the Synic's message page */
> simp.as_uint64 = hv_get_register(HV_REGISTER_SIMP);
> +
> simp.simp_enabled = 1;
>
> - if (hv_isolation_type_snp()) {
> + if (hv_isolation_type_snp() || hv_root_partition) {
> hv_cpu->synic_message_page
> = memremap(simp.base_simp_gpa << HV_HYP_PAGE_SHIFT,
> HV_HYP_PAGE_SIZE, MEMREMAP_WB);
> @@ -233,7 +242,7 @@ void hv_synic_enable_regs(unsigned int cpu)
> siefp.as_uint64 = hv_get_register(HV_REGISTER_SIEFP);
> siefp.siefp_enabled = 1;
>
> - if (hv_isolation_type_snp()) {
> + if (hv_isolation_type_snp() || hv_root_partition) {
> hv_cpu->synic_event_page =
> memremap(siefp.base_siefp_gpa << HV_HYP_PAGE_SHIFT,
> HV_HYP_PAGE_SIZE, MEMREMAP_WB);
> --
> 2.25.1
