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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH for-next 06/16] xen/arm: Extend copy_to_guest to support copying from/to guest physical address
On Thu, 23 Nov 2017, Julien Grall wrote:
> The only differences between copy_to_guest and access_guest_memory_by_ipa are:
> - The latter does not support copying data crossing page boundary
> - The former is copying from/to guest VA whilst the latter from
> guest PA
>
> copy_to_guest can easily be extended to support copying from/to guest
> physical address. For that a new bit is used to tell whether linear
> address or ipa is been used.
>
> Lastly access_guest_memory_by_ipa is reimplemented using copy_to_guest.
> This also has the benefits to extend the use of it, it is now possible
> to copy data crossing page boundary.
>
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Ah! This is the reason why previous patches were not using vaddr_t. It
makes sense now. May I suggest we use something different from paddr_t
in copy_guest for addr type? I don't think is correct to specify addr as
paddr_t when it could be vaddr_t; in the future we could have type
checks on them.
I suggest we specify it as u64, but if you have a better idea go for it.
> ---
> xen/arch/arm/guestcopy.c | 86
> ++++++++++++++++++++++--------------------------
> 1 file changed, 39 insertions(+), 47 deletions(-)
>
> diff --git a/xen/arch/arm/guestcopy.c b/xen/arch/arm/guestcopy.c
> index 487f5ab82d..be53bee559 100644
> --- a/xen/arch/arm/guestcopy.c
> +++ b/xen/arch/arm/guestcopy.c
> @@ -8,6 +8,31 @@
> #define COPY_flush_dcache (1U << 0)
> #define COPY_from_guest (0U << 1)
> #define COPY_to_guest (1U << 1)
> +#define COPY_ipa (0U << 2)
> +#define COPY_linear (1U << 2)
> +
> +static struct page_info *translate_get_page(struct vcpu *v, paddr_t addr,
> + bool linear, bool write)
> +{
> + p2m_type_t p2mt;
> + struct page_info *page;
> +
> + if ( linear )
> + return get_page_from_gva(v, addr, write ? GV2M_WRITE : GV2M_READ);
> +
> + page = get_page_from_gfn(v->domain, paddr_to_pfn(addr), &p2mt,
> P2M_ALLOC);
> +
> + if ( !page )
> + return NULL;
> +
> + if ( !p2m_is_ram(p2mt) )
> + {
> + put_page(page);
> + return NULL;
> + }
> +
> + return page;
> +}
>
> static unsigned long copy_guest(void *buf, paddr_t addr, unsigned int len,
> struct vcpu *v, unsigned int flags)
> @@ -21,8 +46,8 @@ static unsigned long copy_guest(void *buf, paddr_t addr,
> unsigned int len,
> unsigned size = min(len, (unsigned)PAGE_SIZE - offset);
> struct page_info *page;
>
> - page = get_page_from_gva(v, addr,
> - (flags & COPY_to_guest) ? GV2M_WRITE :
> GV2M_READ);
> + page = translate_get_page(v, addr, flags & COPY_linear,
> + flags & COPY_to_guest);
> if ( page == NULL )
> return len;
>
> @@ -63,73 +88,40 @@ static unsigned long copy_guest(void *buf, paddr_t addr,
> unsigned int len,
> unsigned long raw_copy_to_guest(void *to, const void *from, unsigned len)
> {
> return copy_guest((void *)from, (unsigned long)to, len,
> - current, COPY_to_guest);
> + current, COPY_to_guest | COPY_linear);
> }
>
> unsigned long raw_copy_to_guest_flush_dcache(void *to, const void *from,
> unsigned len)
> {
> return copy_guest((void *)from, (unsigned long)to, len,
> - current, COPY_to_guest | COPY_flush_dcache);
> + current, COPY_to_guest | COPY_flush_dcache |
> COPY_linear);
> }
>
> unsigned long raw_clear_guest(void *to, unsigned len)
> {
> - return copy_guest(NULL, (unsigned long)to, len, current, COPY_to_guest);
> + return copy_guest(NULL, (unsigned long)to, len, current,
> + COPY_to_guest | COPY_linear);
> }
>
> unsigned long raw_copy_from_guest(void *to, const void __user *from,
> unsigned len)
> {
> - return copy_guest(to, (unsigned long)from, len, current,
> COPY_from_guest);
> + return copy_guest(to, (unsigned long)from, len, current,
> + COPY_from_guest | COPY_linear);
> }
>
> -/*
> - * Temporarily map one physical guest page and copy data to or from it.
> - * The data to be copied cannot cross a page boundary.
> - */
> int access_guest_memory_by_ipa(struct domain *d, paddr_t gpa, void *buf,
> uint32_t size, bool is_write)
> {
> - struct page_info *page;
> - uint64_t offset = gpa & ~PAGE_MASK; /* Offset within the mapped page */
> - p2m_type_t p2mt;
> - void *p;
> -
> - /* Do not cross a page boundary. */
> - if ( size > (PAGE_SIZE - offset) )
> - {
> - printk(XENLOG_G_ERR "d%d: guestcopy: memory access crosses page
> boundary.\n",
> - d->domain_id);
> - return -EINVAL;
> - }
I don't know if we necessarely care about this, but with this change
this error path goes away. Do we want to keep it?
> - page = get_page_from_gfn(d, paddr_to_pfn(gpa), &p2mt, P2M_ALLOC);
> - if ( !page )
> - {
> - printk(XENLOG_G_ERR "d%d: guestcopy: failed to get table entry.\n",
> - d->domain_id);
> - return -EINVAL;
> - }
> -
> - if ( !p2m_is_ram(p2mt) )
> - {
> - put_page(page);
> - printk(XENLOG_G_ERR "d%d: guestcopy: guest memory should be RAM.\n",
> - d->domain_id);
> - return -EINVAL;
> - }
> + unsigned long left;
> + int flags = COPY_ipa;
>
> - p = __map_domain_page(page);
> + flags |= is_write ? COPY_to_guest : COPY_from_guest;
>
> - if ( is_write )
> - memcpy(p + offset, buf, size);
> - else
> - memcpy(buf, p + offset, size);
> + /* P2M is shared between all vCPUs, so the vcpu used does not matter. */
> + left = copy_guest(buf, gpa, size, d->vcpu[0], flags);
fair enough, then why not use current?
> - unmap_domain_page(p);
> - put_page(page);
> -
> - return 0;
> + return (!left) ? 0 : -EINVAL;
> }
>
> /*
> --
> 2.11.0
>
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