Hi Marc,
On 1/20/23 2:47 AM, Marc Zyngier wrote:
On Thu, 19 Jan 2023 01:11:44 +0000,
Gavin Shan <gshan@xxxxxxxxxx> wrote:
I will have vgic_write_guest_lock() in v2. Note that those 3 paths can't be
running in parallel since one switch is shared by them. Alternatively, we
extend struct vgic_dist::save_tables_in_progress from 'bool' to 'unsigned long'.
Several bit is defined for each site as below. In this way, the 3 paths can be
running in parallel:
unsigned long struct vgic_dist::save_tables_in_progress
#define VGIC_DIST_SAVE_ITS_ITE 0 /* ITS Translation Entry */
#define VGIC_DIST_SAVE_ITS_DTE 1 /* ITS Device Table Entry */
#define VGIC_DIST_SAVE_ITS_CTE 2 /* ITS Collection Table Entry */
#define VGIC_DIST_SAVE_ITS_CT 3 /* ITS Collection Table */
#define VGIC_DIST_SAVE_VGIC3_LPI 4 /* VGIC3 LPI Pending Status */
#define VGIC_DIST_SAVE_VGIC3_PENDING_TABLE 5 /* VGIC3 Pending Table */
The drawback is the calls are limited to 64. If those 3 paths can't be running
in parallel, we needn't the extension at all.
It should all be completely sequential. KVM_DEV_ARM_ITS_SAVE_TABLES
runs in a context where everything is locked, and so is
VGIC_DIST_SAVE_VGIC3_PENDING_TABLE.
Thanks for your confirm. Yeah, it's sequential because 'kvm->lock' is
hold on KVM_DEV_ARM_ITS_SAVE_TABLES and VGIC_DIST_SAVE_VGIC3_PENDING_TABLE.
So all good to have one shared switch. v2 will be posted pretty soon.
Thanks,
Gavin
