Re: [Qemu-devel] [PATCH 2/2] target/i386: sev: Do not pin the ram device memory region

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 17 Jan 2019 21:53:16 +0000
"Singh, Brijesh" <brijesh.singh@amd.com> wrote:

> The RAM device presents a memory region that should be handled
> as an IO region and should not be pinned.
> 
> In the case of the vfio-pci, RAM device represents a MMIO BAR
> and the memory region is not backed by pages hence
> KVM_MEMORY_ENCRYPT_REG_REGION fails to lock the memory range.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1667249
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  target/i386/sev.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index 20b2d325d8..3e9d5c02fa 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -131,6 +131,17 @@ sev_ram_block_added(RAMBlockNotifier *n, void *host, size_t size)
>  {
>      int r;
>      struct kvm_enc_region range;
> +    ram_addr_t offset;
> +    MemoryRegion *mr;
> +
> +    mr = memory_region_from_host(host, &offset);
> +    /*
> +     * The RAM device presents a memory region that should be treated
> +     * as IO region and should not be pinned.
> +     */
> +    if (memory_region_is_ram_device(mr)) {
> +        return;
> +    }
>  
>      range.addr = (__u64)(unsigned long)host;
>      range.size = size;


memory_region_from_host() can return NULL, which would give you a
segfault at memory_region_is_ram_device(), so you might want to test mr
on it's own first and decide which path that would take.  Thanks,

Alex