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HV: io: refine state transitions of VHM requests

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Instead of using two members for maintaining the state of a VHM request, this
patch replaces the transitions with a single state. Basically the lifecycle of a
VHM request shall be:

    FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...

The structure header of vhm_request has more details of the transitions access
limitations under different states.

Also drop the set but unused member vcpu.ioreq_pending.

For backward-compatibility, the obsolete 'valid' member is still kept and
maintained before SOS and DM adapts to the new state transitions.

v2 -> v3:

    * Use complete_ioreq to mark an I/O request finished in
      dm_emulate_(pio|mmio)_post.

Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
This commit is contained in:
Junjie Mao
2018-07-27 21:24:39 +08:00
committed by lijinxia
parent 941eb9db02
commit 17771c0ac2
8 changed files with 144 additions and 51 deletions
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122
hypervisor/include/public/acrn_common.h
View File

@@ -26,8 +26,9 @@
*/
#define VHM_REQUEST_MAX 16U
#define REQ_STATE_FREE 3
#define REQ_STATE_PENDING 0
#define REQ_STATE_SUCCESS 1
#define REQ_STATE_COMPLETE 1
#define REQ_STATE_PROCESSING 2
#define REQ_STATE_FAILED -1
@@ -90,27 +91,122 @@ union vhm_io_request {
int64_t reserved1[8];
};
/* vhm_request are 256Bytes aligned */
/**
* @brief 256-byte VHM requests
*
* The state transitions of a VHM request are:
*
* FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...
* \ /
* +--> FAILED -+
*
* When a request is in COMPLETE or FREE state, the request is owned by the
* hypervisor. SOS (VHM or DM) shall not read or write the internals of the
* request except the state.
*
* When a request is in PENDING or PROCESSING state, the request is owned by
* SOS. The hypervisor shall not read or write the request other than the state.
*
* Based on the rules above, a typical VHM request lifecycle should looks like
* the following.
*
* (assume the initial state is FREE)
*
* SOS vCPU 0 SOS vCPU x UOS vCPU y
*
* hypervisor:
* fill in type, addr, etc.
* pause UOS vcpu y
* set state to PENDING (a)
* fire upcall to SOS vCPU 0
*
* VHM:
* scan for pending requests
* set state to PROCESSING (b)
* assign requests to clients (c)
*
* client:
* scan for assigned requests
* handle the requests (d)
* set state to COMPLETE
* notify the hypervisor
*
* hypervisor:
* resume UOS vcpu y (e)
*
* hypervisor:
* post-work (f)
* set state to FREE
*
* Note that the following shall hold.
*
* 1. (a) happens before (b)
* 2. (c) happens before (d)
* 3. (e) happens before (f)
* 4. One vCPU cannot trigger another I/O request before the previous one has
* completed (i.e. the state switched to FREE)
*
* Accesses to the state of a vhm_request shall be atomic and proper barriers
* are needed to ensure that:
*
* 1. Setting state to PENDING is the last operation when issuing a request in
* the hypervisor, as the hypervisor shall not access the request any more.
*
* 2. Due to similar reasons, setting state to COMPLETE is the last operation
* of request handling in VHM or clients in SOS.
*
* The state FAILED is an obsolete state to indicate that the I/O request cannot
* be handled. In such cases the mediators and DM should switch the state to
* COMPLETE with the value set to all 1s for read, and skip the request for
* writes. This state WILL BE REMOVED after the mediators and DM are updated to
* follow this rule.
*/
struct vhm_request {
/* offset: 0bytes - 63bytes */
/**
* Type of this request.
*
* Byte offset: 0.
*/
uint32_t type;
int32_t reserved0[15];
/* offset: 64bytes-127bytes */
/**
* Reserved.
*
* Byte offset: 4.
*/
uint32_t reserved0[15];
/**
* Details about this request. For REQ_PORTIO, this has type
* pio_request. For REQ_MMIO and REQ_WP, this has type mmio_request. For
* REQ_PCICFG, this has type pci_request.
*
* Byte offset: 64.
*/
union vhm_io_request reqs;
/* True: valid req which need VHM to process.
* ACRN write, VHM read only
**/
/**
* Whether this request is valid for processing. ACRN write, VHM read
* only.
*
* Warning; this field is obsolete and will be removed soon.
*
* Byte offset: 128.
*/
int32_t valid;
/* the client which is distributed to handle this request */
/**
* The client which is distributed to handle this request. Accessed by
* VHM only.
*
* Byte offset: 132.
*/
int32_t client;
/* 1: VHM had processed and success
* 0: VHM had not yet processed
* -1: VHM failed to process. Invalid request
* VHM write, ACRN read only
/**
* The status of this request, taking REQ_STATE_xxx as values.
*
* Byte offset: 136.
*/
int32_t processed;
} __aligned(256);