Re: [PATCH v2 08/17] x86/hyperv: handling hypercall page setup for root
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: 2020-11-12 15:51:20
Also in:
linux-hyperv, lkml
Wei Liu [off-list ref] 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. The suspend, resume and cleanup paths remain untouched because they are not supported in this setup yet.
What about adding BUG_ONs there then?
quoted hunk
Signed-off-by: Lillian Grassin-Drake <redacted> Signed-off-by: Sunil Muthuswamy <redacted> Signed-off-by: Nuno Das Neves <redacted> Co-Developed-by: Lillian Grassin-Drake <redacted> Co-Developed-by: Sunil Muthuswamy <redacted> Co-Developed-by: Nuno Das Neves <redacted> Signed-off-by: Wei Liu <wei.liu@kernel.org> --- arch/x86/hyperv/hv_init.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-)diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index 73b0fb851f76..9fcaf741be99 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;@@ -438,8 +439,35 @@ 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, PAGE_SIZE);
Super-nit: while on x86 PAGE_SIZE always matches HV_HYP_PAGE_SIZE, would it be more accurate to use the later here?
+ 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-- Vitaly _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization