RE: [PATCH v5 08/16] x86/hyperv: handling hypercall page setup for root

Michael Kelley
2021-01-26T10:39:46Z

From: Wei Liu <wei.liu@kernel.org> Sent: Wednesday, January 20, 2021 4:01 AM
>
> When Linux is running as the root partition, the hypercall page will
> have already been setup by Hyper-V. Copy the content over to the
> allocated page.
>
> Add checks to hv_suspend & co to bail early because they are not
> supported in this setup yet.
>
> Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> Co-Developed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
> Co-Developed-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
> v3:
> 1. Use HV_HYP_PAGE_SIZE.
> 2. Add checks to hv_suspend & co.
> ---
> arch/x86/hyperv/hv_init.c | 37 ++++++++++++++++++++++++++++++++++---
> 1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index fc9941bd8653..ad8e77859b32 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -25,6 +25,7 @@
> #include <linux/cpuhotplug.h>
> #include <linux/syscore_ops.h>
> #include <clocksource/hyperv_timer.h>
> +#include <linux/highmem.h>
>
> u64 hv_current_partition_id = ~0ull;
> EXPORT_SYMBOL_GPL(hv_current_partition_id);
> @@ -283,6 +284,9 @@ static int hv_suspend(void)
> union hv_x64_msr_hypercall_contents hypercall_msr;
> int ret;
>
> + if (hv_root_partition)
> + return -EPERM;
> +
> /*
> * Reset the hypercall page as it is going to be invalidated
> * accross hibernation. Setting hv_hypercall_pg to NULL ensures
> @@ -433,8 +437,35 @@ void __init hyperv_init(void)
>
> rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> hypercall_msr.enable = 1;
> - hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
> - wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +
> + if (hv_root_partition) {
> + struct page *pg;
> + void *src, *dst;
> +
> + /*
> + * For the root partition, the hypervisor will set up its
> + * hypercall page. The hypervisor guarantees it will not show
> + * up in the root's address space. The root can't change the
> + * location of the hypercall page.
> + *
> + * Order is important here. We must enable the hypercall page
> + * so it is populated with code, then copy the code to an
> + * executable page.
> + */
> + wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> +
> + pg = vmalloc_to_page(hv_hypercall_pg);
> + dst = kmap(pg);
> + src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT,
> PAGE_SIZE,
> + MEMREMAP_WB);
> + BUG_ON(!(src && dst));
> + memcpy(dst, src, HV_HYP_PAGE_SIZE);
> + memunmap(src);
> + kunmap(pg);
> + } else {
> + hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
> + wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> + }
>
> /*
> * Ignore any errors in setting up stimer clockevents
> @@ -577,6 +608,6 @@ EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);
>
> bool hv_is_hibernation_supported(void)
> {
> - return acpi_sleep_state_supported(ACPI_STATE_S4);
> + return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
> }
> EXPORT_SYMBOL_GPL(hv_is_hibernation_supported);
> --
> 2.20.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>