[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH 2/3] x86/clang: add retpoline support


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Wed, 16 Feb 2022 12:26:42 +0100
  • Arc-authentication-results: i=1; mx.microsoft.com 1; spf=none; dmarc=none; dkim=none; arc=none
  • Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=ABOy2eIDdsp6vK3CxREgVkNbS5AWcW3H7w/PlWtH0JY=; b=jCv0H6XvGs6paO9fo96nxByHd7XXFEmmsZ+p9QF6chZMDKH2mbaNh/m8DuywCjl2CW445RbWSOFxzTDdMfyMbtEPPm2ABAB1+eanliOz+fpRXrtJhC55qJNl8NkW6lRqXV1TL4nZ3gYtomubu1RRax3C0760icAMb8VOuk23CRFloeYkkko63Mpr2PLL9tHiPWV7RdO+T9T5RjhNk5qm79Cr1dH2ViKR9VXNQSXP2m0kJS54cKfpc7p+ePZzZvjFs3u5nAol1zfj9abnmkd/bTkpjVY8tSFua4wFWGtWMG+cLbktYIqT0Tds2hbyqUXKFLotCNpXvkHQMCp5xacdqQ==
  • Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=ACY9VyE2kkPwYe4gnc2If7g4LE2+CPOrmksYDTutFte25hkbR7mbfclVP3YwQs44qYAWDcCzPwgws86DPxsru6SQahU2h3eH0tbRm4dRYJg0mdQhkOqTHVf8XjiMY0uPTR6niROF7dc6ONCNVZ44UiMHTVfg++zUkiPt8XcRJqudZ8HOASE1Dda9V2N5T41JvCLqu5tT2Ymja406wTM6EZun4S7N6dMicyNqz85HNEQf+HLT30CZPdIyEbW5sOPLlK7E7VlfS+WX3vD8pnheEjx5X+4T1tgIx/WcwCTxuOmHDxk97+EY7SAdwKGrvvaBmnukyOwqro1oSDH7B5xQ4g==
  • Authentication-results: esa3.hc3370-68.iphmx.com; dkim=pass (signature verified) header.i=@citrix.onmicrosoft.com
  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 16 Feb 2022 11:27:02 +0000
  • Ironport-data: A9a23:pcbNbazWmVGdxO6cKSd6t+frwSrEfRIJ4+MujC+fZmUNrF6WrkUHn zQfDW2BPPjYamegKox2bIS+p08EvpHczoJgTQJvqiAxQypGp/SeCIXCJC8cHc8zwu4v7q5Dx 59DAjUVBJlsFhcwnvopW1TYhSEUOZugH9IQM8aZfHAhLeNYYH1500g7wbdn2tcAbeWRWGthh /uj+6UzB3f9s9JEGjp8B3Wr8U4HUFza4Vv0j3RmDRx5lAa2e0o9VfrzEZqZPXrgKrS4K8bhL wr1IBNVyUuCl/slIovNfr8W6STmSJaKVeSFoiI+t6RPHnGuD8H9u0o2HKN0VKtZt9mGt8hj5 9VUlKWvcgQWJ6iPqM05YR14HwgraMWq+JefSZS+mcmazkmAeHrw2fR+SkoxOOX0+M4uXzsIr 6ZBbmlQMFbT3Ipaw5riIgVort4kI8TxepsWp1lrzC3DDOZgSpfGK0nPzYEEh2xo25kXdRrYT 8EXdWs2TRHCWRpCfQslCooQzc2SlnaqJlW0r3rK/PFqsgA/1jdZwLXrddbYZNGObcFUhVqD4 HLL+XzjBRMXP8DZziCKmlqzgsffkCW9X5gdfJW6/PN3hFyYxkQIFQYbE1C8pJGEZlWWAowFb RZOo2x38PZ0pBfDosTBswOQuGyrvgc9YsVrENIj7UK9447m5yaVLz1RJtJeU+AOuMgzTD0s8 1aGmdL1GDBi2IGopWKhGqS89m3rZ3VMRYMWTWpdFFZevYG/yG0mpk+XFr5e/LiJYsoZ8N0a6 xSDt2AAiroalqbnPI3rrAmc01pASnUkJzPZBzk7vEr4tmuVh6b/PuREDGQ3C94ace51qXHb4 RA5dzC2trxmMH10vHXlrB8xNL+o/e2ZFzbXnERiGZIsnxz0pSL/LN0JumAvdR4zWirhRdMPS BWO0e+2zMUNVEZGkIctO97hYyjU5fSI+SvZugD8MYMVP8kZmP6v9yByf0+At10BY2B3+ZzTz ayzKJ72ZV5DUPwP5GPvG481jO96rghjlDi7bc2qkHyaPU+2OSf9pUEtawDVMIjULcqs/W3oz jqoH5Ham08EAbKkO3S/HEx6BQliEEXXzKve8qR/XuWCPhBnCCcmDfrQyqkmYItrg+JekeKgw 513chYwJIPXiSKVJAOURGpkbb+zD59zoWhiZX4nPEqy2mhlaoGqtf9Ne5wydLgh1epi0f8rE KVVJ5TeWqxCGmbd5jAQTZjht4g+Jh6lsh2DYni+az8lcp8+GwGQoo34fhHi/TUlBzassZdsu KWp0w7WGMJRRwlrAMvMRuioyle94SoUlO5oBhOaKdhPYkT8toNtLnWp3PMwJsgNLzTFxyebi FnKUUtJ+7GVrtZsotfThK2Co4O4KMdEHxJXTzvB8LK7FSjG5W7/k4VOZ/mFIGLGX2Tu9aT8O egMl6PgMOcKlUphupZnF+o51ro34tbiquMIzglgG3mXPV2nBqk5fyuD1MhL8KZM2qVYqU29X UfWootWPrCAOcXEFl8NJVV6MrTfhK9MwjSCv+4oJEja5TNs+OvVWEpfCBCAlShBIeYnK4gi2 +og5JYb5gHXZsDG6TpaYvS4L1ixE0E=
  • Ironport-hdrordr: A9a23:E/zKa6tg39OZSLyYgS9MLfYr7skDctV00zEX/kB9WHVpm6uj5q eTdZUgpHvJYVMqM03I9urtBEDtexzhHP1OgbX5X43NYOCOggLBRuxfBODZogHIKmnT8fNcyL clU4UWMqyUMbGit7eY3OBvKadD/OW6
  • Ironport-sdr: MzalmwrdxonjexbZ6CXgALhsRdjii26eAsK6C44GTRioSNQiyqZBDnPTnh5H7l/4/e4Qfo9p5D dJ4kzQlr1n4icp7blgZ3gypM/dEDXtM442T+DpERMXgtAyp4iAkEhl3Ds3N4THRjT3Kql8PX6B AnYUL6AXtf18nET2OVCNGPpU1BDc2EZkgwv8prFDoT5PYZijIUvDJyPSAkmNNLRjWzN+a15FlX sFOoaDwQ0a6soRPblGGWAJlLP6o3MQ8+ZroDumv48wRqX0/3gExasTxvccyspXnWUEsCM7xWmP MuSxwvlTp8huk4scjW+k9L8r
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Wed, Feb 16, 2022 at 10:47:52AM +0100, Jan Beulich wrote:
> On 16.02.2022 10:02, Roger Pau Monne wrote:
> > Detect whether the compiler supports clang retpoline option and enable
> > by default if available, just like it's done for gcc.
> > 
> > Note clang already disables jump tables when retpoline is enabled, so
> > there's no need to also pass the fno-jump-tables parameter.
> 
> That's one of the secondary gcc side arrangements. What about the other
> (-mindirect-branch-register)?

clang already passes the return address on a register always on amd64
so that's not needed either. I can add a comment like I've done for
no-jump-tables.

> > Reported-by: Jan Beulich <JBeulich@xxxxxxxx>
> 
> That's Andrew, not me?

Ops, sorry, I got that mixed up then.

Thanks, Roger.



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.