[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v8 3/5] x86/ioreq server: Handle read-modify-write cases for p2m_ioreq_server pages.
In ept_handle_violation(), write violations are also treated as read violations. And when a VM is accessing a write-protected address with read-modify-write instructions, the read emulation process is triggered first. For p2m_ioreq_server pages, current ioreq server only forwards the write operations to the device model. Therefore when such page is being accessed by a read-modify-write instruction, the read operations should be emulated here in hypervisor. This patch provides such a handler to copy the data to the buffer. Note: MMIOs with p2m_mmio_dm type do not need such special treatment because both reads and writes will go to the device mode. Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> --- Cc: Paul Durrant <paul.durrant@xxxxxxxxxx> Cc: Jan Beulich <jbeulich@xxxxxxxx> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> changes in v2: - According to comments from Jan: clarify comments in hvmemul_do_io(). changes in v2: - According to comments from Jan: rename mem_ops to ioreq_server_ops. - According to comments from Jan: use hvm_copy_from_guest_phys() in ioreq_server_read(), instead of do it by myself. --- xen/arch/x86/hvm/emulate.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c index 37139e6..52c726e 100644 --- a/xen/arch/x86/hvm/emulate.c +++ b/xen/arch/x86/hvm/emulate.c @@ -94,6 +94,26 @@ static const struct hvm_io_handler null_handler = { .ops = &null_ops }; +static int ioreq_server_read(const struct hvm_io_handler *io_handler, + uint64_t addr, + uint32_t size, + uint64_t *data) +{ + if ( hvm_copy_from_guest_phys(data, addr, size) != HVMCOPY_okay ) + return X86EMUL_UNHANDLEABLE; + + return X86EMUL_OKAY; +} + +static const struct hvm_io_ops ioreq_server_ops = { + .read = ioreq_server_read, + .write = null_write +}; + +static const struct hvm_io_handler ioreq_server_handler = { + .ops = &ioreq_server_ops +}; + static int hvmemul_do_io( bool_t is_mmio, paddr_t addr, unsigned long *reps, unsigned int size, uint8_t dir, bool_t df, bool_t data_is_addr, uintptr_t data) @@ -193,6 +213,9 @@ static int hvmemul_do_io( * - If the domain ioreq_server is NULL, assume there is a * race between the unbinding of ioreq server and guest fault * so re-try the instruction. + * + * - If the accesss is a read, this could be part of a + * read-modify-write instruction, emulate the read first. */ struct hvm_ioreq_server *s = NULL; p2m_type_t p2mt = p2m_invalid; @@ -226,6 +249,17 @@ static int hvmemul_do_io( vio->io_req.state = STATE_IOREQ_NONE; break; } + + /* + * This is part of a read-modify-write instruction. + * Emulate the read part so we have the value cached. + */ + if ( dir == IOREQ_READ ) + { + rc = hvm_process_io_intercept(&ioreq_server_handler, &p); + vio->io_req.state = STATE_IOREQ_NONE; + break; + } } } -- 1.9.1 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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