From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [v4 04/17] iommu: Add iommu_intpost to control VT-d Posted-Interrupts feature Date: Thu, 23 Jul 2015 15:05:16 +0100 Message-ID: <55B0F49C.7030605@citrix.com> References: <1437651353-5275-1-git-send-email-feng.wu@intel.com> <1437651353-5275-5-git-send-email-feng.wu@intel.com> <55B0F3D7.5080302@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55B0F3D7.5080302@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Feng Wu , xen-devel@lists.xen.org Cc: Kevin Tian , Jan Beulich List-Id: xen-devel@lists.xenproject.org On 23/07/15 15:01, Andrew Cooper wrote: > On 23/07/15 12:35, Feng Wu wrote: >> VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt. >> With VT-d Posted-Interrupts enabled, external interrupts from >> direct-assigned devices can be delivered to guests without VMM >> intervention when guest is running in non-root mode. >> >> This patch adds variable 'iommu_intpost' to control whether enable VT-d >> posted-interrupt or not in the generic IOMMU code. >> >> CC: Jan Beulich >> CC: Kevin Tian >> Signed-off-by: Feng Wu >> Reviewed-by: Kevin Tian > Please patch docs/misc/xen-command-line.markdown as you are > >> --- >> v4: >> - No changes >> >> v3: >> - Remove pointless initializer for 'iommu_intpost'. >> - Some adjustment for "if no intremap then no intpost" logic. >> * For parse_iommu_param(), move it to the end of the function, >> so we don't need to add the some logic when introduing the >> new kernel parameter 'intpost' in later patch. >> * Add this logic in iommu_setup() after iommu_hardware_setup() >> is called. >> >> xen/drivers/passthrough/iommu.c | 17 ++++++++++++++++- >> xen/include/xen/iommu.h | 2 +- >> 2 files changed, 17 insertions(+), 2 deletions(-) >> >> diff --git a/xen/drivers/passthrough/iommu.c b/xen/drivers/passthrough/iommu.c >> index 06cb38f..536b69f 100644 >> --- a/xen/drivers/passthrough/iommu.c >> +++ b/xen/drivers/passthrough/iommu.c >> @@ -39,6 +39,7 @@ static void iommu_dump_p2m_table(unsigned char key); >> * no-snoop Disable VT-d Snoop Control >> * no-qinval Disable VT-d Queued Invalidation >> * no-intremap Disable VT-d Interrupt Remapping >> + * no-intpost Disable VT-d Interrupt posting >> */ >> custom_param("iommu", parse_iommu_param); >> bool_t __initdata iommu_enable = 1; >> @@ -51,6 +52,14 @@ bool_t __read_mostly iommu_passthrough; >> bool_t __read_mostly iommu_snoop = 1; >> bool_t __read_mostly iommu_qinval = 1; >> bool_t __read_mostly iommu_intremap = 1; >> + >> +/* >> + * In the current implementation of VT-d posted interrupts, in some extreme >> + * cases, the per cpu list which saves the blocked vCPU will be very long, >> + * and this will affect the interrupt latency, so let this feature off by >> + * default until we find a good solution to resolve it. >> + */ >> +bool_t __read_mostly iommu_intpost; >> bool_t __read_mostly iommu_hap_pt_share = 1; >> bool_t __read_mostly iommu_debug; >> bool_t __read_mostly amd_iommu_perdev_intremap = 1; >> @@ -112,6 +121,9 @@ static void __init parse_iommu_param(char *s) >> >> s = ss + 1; >> } while ( ss ); >> + >> + if ( !iommu_intremap ) >> + iommu_intpost = 0; > This hunk is still wrong, as I said in v3. Furthermore, you appear to have no way in v4 to enable intpost on the Xen command line. ~Andrew