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SubjectRe: [PATCH RFC v1 08/18] x86/hyperv: handling hypercall page setup for root
Date
Wei Liu <wei.liu@kernel.org> writes:

> 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.

And we can't setup a new hypercall page by writing something different
to HV_X64_MSR_HYPERCALL, right?

>
> The suspend, resume and cleanup paths remain untouched 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 <nudasnev@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 <nudasnev@microsoft.com>
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
> arch/x86/hyperv/hv_init.c | 26 ++++++++++++++++++++++++--
> 1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 0eec1ed32023..26233aebc86c 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>
>
> /* Is Linux running as the root partition? */
> bool hv_root_partition;
> @@ -448,8 +449,29 @@ 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;
> +
> + /*
> + * 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);

memremap() can fail...

> + memcpy(dst, src, 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);
> + }

Why can't we do wrmsrl() for both cases here?

>
> /*
> * Ignore any errors in setting up stimer clockevents

--
Vitaly

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